diff --git a/rack.bracket/LICENSE.txt b/rack.bracket/LICENSE.txt
new file mode 100644
index 0000000..c04ad7a
--- /dev/null
+++ b/rack.bracket/LICENSE.txt
@@ -0,0 +1 @@
+This thing was created by Thingiverse user russross, and is licensed under cc-nc.
\ No newline at end of file
diff --git a/rack.bracket/README.txt b/rack.bracket/README.txt
new file mode 100644
index 0000000..50945af
--- /dev/null
+++ b/rack.bracket/README.txt
@@ -0,0 +1 @@
+Raspberry Pi 4 2U rack-mount bracket by russross on Thingiverse: https://www.thingiverse.com/thing:4078710
\ No newline at end of file
diff --git a/rack.bracket/raspberry-pi-rack-ears.scad b/rack.bracket/raspberry-pi-rack-ears.scad
new file mode 100644
index 0000000..e52ea62
--- /dev/null
+++ b/rack.bracket/raspberry-pi-rack-ears.scad
@@ -0,0 +1,221 @@
+/* [Bolt holes in the corners] */
+
+// Pick the size of the long threaded rods that run through
+// the corners and hold everything together.
+//
+// These are the sizes that are commonly available at
+// Home Depot or Lowes:
+//
+// 1/4 inch: 3.175
+// #12     : 2.778125
+// #10     : 2.38125 (default and recommended)
+//
+// Note: you should pick the same size and fudge factor
+// for the frame parts.
+bolt_size = 2.38125;
+
+// Make the bolt holes this much bigger than the size of the bolt
+// to give a more comfortable fit
+bolt_hole_fudge = 0.2; // [0:0.25:1]
+
+
+/* [Notches for attaching to the frame parts] */
+
+// You can optionally omit the notches for one ear that will
+// join with a frame on the side that has no tabs.
+// For the the other you should leave this at its default of true.
+notches_enabled = true;
+
+// Make the slot this much taller than the tabs
+// to give a more comfortable fit.
+notch_fudge = 0.3; // [0:0.25:1]
+
+
+/* [Bolt holes for mounting to the rack] */
+
+// The size of the bolt holes for mounting to the server rack.
+// The default is for M6 bolts.
+ear_bolt_size = 3;
+
+// Make the ear bolt holes this much longer than they are wide
+// in case the entire assembled rack is not precisely the right
+// length.
+ear_bolt_stretch = 3;
+
+
+/* [Hidden] */
+
+width = 82;
+length = 90;
+height = 5;
+frame_width = 15.875;
+distance_to_frame = 10;
+distance_between_bolt_holes = 15.875 * 2 + 12.7;
+ear_height = distance_to_frame + frame_width;
+
+notch_height = 2;
+outer_wall_thickness = 12;
+inner_wall_thickness = 7;
+back_wall_thickness = 5;
+wall_diff = outer_wall_thickness - inner_wall_thickness;
+floor_depth = 3;
+tray_depth = 5;
+tray_slot_depth = 2.5;
+spacer_depth = 3;
+epsilon = 0.001;
+
+sd_window_width = 40;
+sd_window_height = height - (tray_depth + floor_depth)*2;
+near_pillar_width = 15;
+far_pillar_width = 10;
+floor_window_width = sd_window_width;
+floor_window_border = (width - floor_window_width - outer_wall_thickness*2) / 2;
+floor_window_length = length - back_wall_thickness - floor_window_border*2;
+port_window_width = length - near_pillar_width - far_pillar_width;
+port_window_frame_height = floor_depth + tray_depth + spacer_depth - notch_height;
+
+bolt_radius = bolt_size + bolt_hole_fudge;
+
+ear_bolt_radius = ear_bolt_size + bolt_hole_fudge;
+floor_mini_window_width = (floor_window_width - floor_window_border) / 2;
+floor_mini_window_length = (floor_window_length - floor_window_border) / 2;
+
+difference() {
+    union() {
+        // the main tray block
+        translate([0, -epsilon, 0]) {
+            cube([width, length + epsilon, height]);
+        }
+        
+        // the ear
+        translate([0, -height, 0]) {
+            cube([width, height, ear_height]);
+        }
+        
+        // reinforce the joint
+        translate([0, 0, 0]) {
+            rotate([45, 0, 0]) {
+                cube([width, height-0.5, height-0.5]);
+            }
+        }
+        
+        translate([ (width - distance_between_bolt_holes)/2 - ear_bolt_radius, 0, 0]) {
+            rotate([45, 0, 0]) {
+                cube([distance_between_bolt_holes + 2*ear_bolt_radius, height+1, height+1]);
+            }
+        }
+    }
+    
+    // cut the bolt holes
+    for (a=[[outer_wall_thickness/2, near_pillar_width/2],
+            [outer_wall_thickness/2, length - far_pillar_width/2],
+            [width - outer_wall_thickness/2, near_pillar_width/2],
+            [width - outer_wall_thickness/2, length - far_pillar_width/2]]) {
+        translate([a[0], a[1], -epsilon]) {
+            cylinder(   h=height + 2*epsilon,
+                        r=bolt_radius,
+                        center=false,
+                        $fn=360);
+        }
+    }
+
+    // make the sides thinner
+    polyhedron(
+        points = [
+            [ wall_diff, length-far_pillar_width-wall_diff, height+notch_height+epsilon],
+            [ wall_diff, near_pillar_width+wall_diff,       height+notch_height+epsilon],
+            [ wall_diff, length-far_pillar_width-wall_diff, -epsilon],
+            [ wall_diff, near_pillar_width+wall_diff,       -epsilon],
+            [-wall_diff, length-far_pillar_width+wall_diff, height+notch_height+epsilon],
+            [-wall_diff, near_pillar_width-wall_diff,       height+notch_height+epsilon],
+            [-wall_diff, length-far_pillar_width+wall_diff, -epsilon],
+            [-wall_diff, near_pillar_width-wall_diff,       -epsilon]
+        ],
+        faces = [
+            [1,0,2,3],
+            [4,5,7,6],
+            [0,4,6,2],
+            [6,7,3,2],
+            [7,5,1,3],
+            [5,4,0,1]
+        ],
+        convexity = 10);
+    polyhedron(
+        points = [
+            [width-wall_diff, near_pillar_width+wall_diff,       height+notch_height+epsilon],
+            [width-wall_diff, length-far_pillar_width-wall_diff, height+notch_height+epsilon],
+            [width-wall_diff, near_pillar_width+wall_diff,       -epsilon],
+            [width-wall_diff, length-far_pillar_width-wall_diff, -epsilon],
+            [width+wall_diff, near_pillar_width-wall_diff,       height+notch_height+epsilon],
+            [width+wall_diff, length-far_pillar_width+wall_diff, height+notch_height+epsilon],
+            [width+wall_diff, near_pillar_width-wall_diff,       -epsilon],
+            [width+wall_diff, length-far_pillar_width+wall_diff, -epsilon]
+        ],
+        faces = [
+            [1,0,2,3],
+            [4,5,7,6],
+            [0,4,6,2],
+            [6,7,3,2],
+            [7,5,1,3],
+            [5,4,0,1]
+        ],
+        convexity = 10);
+
+    if (notches_enabled) {
+        // cut the notches
+        translate([ wall_diff - epsilon,
+                    near_pillar_width + wall_diff,
+                    -epsilon]) {
+            cube([  inner_wall_thickness-2 + epsilon,
+                    length - near_pillar_width - far_pillar_width - 2*wall_diff,
+                    notch_height + notch_fudge + epsilon]);
+        }
+        translate([ width - wall_diff - (inner_wall_thickness-2),
+                    near_pillar_width + wall_diff,
+                    -epsilon]) {
+            cube([  inner_wall_thickness-2 + epsilon,
+                    length - near_pillar_width - far_pillar_width - 2*wall_diff,
+                    notch_height + notch_fudge + epsilon]);
+        }
+    }
+    
+    // cut some mini windows in the floor
+    for (a=[[outer_wall_thickness + floor_window_border,
+                floor_window_border],
+            [width - outer_wall_thickness - floor_window_border - floor_mini_window_width,
+                floor_window_border],
+            [outer_wall_thickness + floor_window_border,
+                2*floor_window_border + floor_mini_window_length],
+            [width - outer_wall_thickness - floor_window_border - floor_mini_window_width,
+                2*floor_window_border + floor_mini_window_length]]) {
+        translate([a[0], a[1], -epsilon]) {
+            cube([  floor_mini_window_width,
+                    floor_mini_window_length,
+                    height + 2*epsilon]);
+        }
+    }
+    
+    // cut the bolt holes on the ear
+    for (a=[    width/2 - distance_between_bolt_holes/2,
+                width/2 + distance_between_bolt_holes/2]) {
+        for (b=[-ear_bolt_stretch/2, ear_bolt_stretch/2]) {
+            translate([ a,
+                        -height-epsilon,
+                        ear_height - frame_width/2 + b]) {
+                rotate([-90,0,0]) {
+                    cylinder(   h=height + 2*epsilon,
+                                r=ear_bolt_radius,
+                                center=false,
+                                $fn=360);
+                }
+            }
+        }
+        translate([ a - ear_bolt_radius,
+                    -height-epsilon,
+                    ear_height - frame_width/2 - ear_bolt_stretch/2]) {
+            cube([  ear_bolt_radius*2,
+                    height + 2*epsilon,
+                    ear_bolt_stretch]);
+        }
+    }
+}
\ No newline at end of file
diff --git a/rack.bracket/raspberry-pi-rack-frame.scad b/rack.bracket/raspberry-pi-rack-frame.scad
new file mode 100644
index 0000000..1b8a188
--- /dev/null
+++ b/rack.bracket/raspberry-pi-rack-frame.scad
@@ -0,0 +1,255 @@
+/* [Bolt holes in the corners] */
+
+// Pick the size of the long threaded rods that run through
+// the corners and hold everything together.
+//
+// These are the sizes that are commonly available at
+// Home Depot or Lowes:
+//
+// 1/4 inch: 3.175
+// #12     : 2.778125
+// #10     : 2.38125 (default and recommended)
+//
+// Note: you should pick the same size and fudge factor
+// for the ear parts.
+bolt_size = 2.38125;
+
+// Make the bolt holes this much bigger than the size of the bolt
+// to give a more comfortable fit
+bolt_hole_fudge = 0.2; // [0:0.25:1]
+
+
+/* [Notches and tabs for stacking] */
+
+// You can optionally omit the notches for the frame on the end
+// that joins with an ear with no tabs. For all of the others
+// you should leave this at its default of true.
+notches_enabled = true;
+
+// Make the slot this much taller than the tabs
+// to give a more comfortable fit.
+notch_fudge = 0.3; // [0:0.25:1]
+
+
+/* [Size] */
+
+// The default is to fit 12 units with PoE hats in a standard rack.
+// 12 is a good fit, and it works nicely with many PoE switches, which
+// often come with 12 or 24 ports. You can bump it up to 13 units and
+// they will still fit nicely with PoE hats, or you can go up to 14
+// of you are not using the hats.
+number_to_fit = 12; // [12:Relaxed fit, 13:Using PoE, 14:Without PoE hats]
+
+/* [Hidden] */
+// make the screw holes this much bigger than the
+// actual screw for a more comfortable fit
+// (a bigger number here will make the screws fit looser)
+screw_hole_fudge = 0.15;
+
+height = (450.85 - 20) / number_to_fit;
+
+width = 82;
+length = 90;
+
+// The height of the notches and tabs
+notch_height = 2;
+
+// epsilon is used to slightly overlap pieces to help the previewer
+epsilon = 0.001;
+
+bolt_radius = bolt_size + bolt_hole_fudge;
+
+outer_wall_thickness = 12;
+inner_wall_thickness = 7;
+back_wall_thickness = 5;
+wall_diff = outer_wall_thickness - inner_wall_thickness;
+floor_depth = 3;
+tray_depth = 5;
+tray_slot_depth = 2.5;
+spacer_depth = 3;
+
+sd_window_width = 40;
+sd_window_height = height - (tray_depth + floor_depth)*2;
+near_pillar_width = 15;
+far_pillar_width = 10;
+floor_window_width = sd_window_width;
+floor_window_border = (width - floor_window_width - outer_wall_thickness*2) / 2;
+floor_window_length = length - back_wall_thickness - floor_window_border*2;
+port_window_width = length - near_pillar_width - far_pillar_width;
+port_window_frame_height = floor_depth + tray_depth + spacer_depth - notch_height;
+
+difference() {
+    union() {
+        // the main block
+        cube([width, length, height]);
+        
+        // the tabs
+        translate([ wall_diff,
+                    near_pillar_width + wall_diff,
+                    height - epsilon]) {
+            cube([  inner_wall_thickness - 2,
+                    length - near_pillar_width - far_pillar_width - wall_diff*2,
+                    notch_height + epsilon]);
+        }
+        translate([ width - outer_wall_thickness + 2,
+                    near_pillar_width + wall_diff,
+                    height - epsilon]) {
+            cube([  inner_wall_thickness - 2,
+                    length - near_pillar_width - far_pillar_width - wall_diff*2,
+                    notch_height + epsilon]);
+        }
+    }
+
+    // carve out the interior
+    translate([outer_wall_thickness, -epsilon, floor_depth]) {
+        cube(  [width - outer_wall_thickness*2,
+                length - back_wall_thickness + epsilon,
+                height + notch_height - floor_depth + epsilon]);
+    }
+
+    // punch a hole for the sd card
+    translate([ (width - sd_window_width) / 2,
+                length - back_wall_thickness - epsilon,
+                tray_depth + floor_depth]) {
+        cube([  sd_window_width,
+                back_wall_thickness + 2*epsilon,
+                height - port_window_frame_height - tray_depth - floor_depth + notch_height]);
+    }
+
+    // punch a hole for side port access
+    translate([ -epsilon,
+                near_pillar_width,
+                port_window_frame_height + notch_height]) {
+        cube([  width + 2*epsilon,
+                port_window_width,
+                height - port_window_frame_height*2]);
+    }
+
+    // punch a hole in the bottom
+    translate([ outer_wall_thickness + floor_window_border,
+                floor_window_border,
+                -epsilon]) {
+        cube([  floor_window_width,
+                floor_window_length,
+                floor_depth + 2*epsilon]);
+    }
+    
+    // open a groove that the speaker jack can slide through
+    translate([ outer_wall_thickness - 2,
+                -epsilon,
+                port_window_frame_height + notch_height]) {
+        cube([  2 + epsilon,
+                near_pillar_width + 2*epsilon,
+                8]);
+    }
+    
+    // soften the leading edge a bit
+    translate([ outer_wall_thickness,
+                0,
+                floor_depth-0.5]) {
+        rotate([25,0,0]) {
+            cube([  width - outer_wall_thickness*2,
+                    2,
+                    2]);
+        }
+    }
+
+    if (notches_enabled) {
+        // cut the notches in the bottom
+        translate([ -epsilon,
+                    near_pillar_width + wall_diff,
+                    -epsilon]) {
+            cube([  outer_wall_thickness - 2 + epsilon,
+                    length - near_pillar_width - far_pillar_width - wall_diff*2,
+                    notch_height + notch_fudge + epsilon]);
+        }
+        translate([ width - outer_wall_thickness + 2,
+                    near_pillar_width + wall_diff,
+                    -epsilon]) {
+            cube([  outer_wall_thickness - 2 + epsilon,
+                    length - near_pillar_width - far_pillar_width - wall_diff*2,
+                    notch_height + notch_fudge + epsilon]);
+        }
+    }
+
+    // cut out the sides to make them thinner
+    polyhedron(
+        points = [
+            [ wall_diff, length-far_pillar_width-wall_diff, height+notch_height+epsilon],
+            [ wall_diff, near_pillar_width+wall_diff,       height+notch_height+epsilon],
+            [ wall_diff, length-far_pillar_width-wall_diff, -epsilon],
+            [ wall_diff, near_pillar_width+wall_diff,       -epsilon],
+            [-wall_diff, length-far_pillar_width+wall_diff, height+notch_height+epsilon],
+            [-wall_diff, near_pillar_width-wall_diff,       height+notch_height+epsilon],
+            [-wall_diff, length-far_pillar_width+wall_diff, -epsilon],
+            [-wall_diff, near_pillar_width-wall_diff,       -epsilon]
+        ],
+        faces = [
+            [1,0,2,3],
+            [4,5,7,6],
+            [0,4,6,2],
+            [6,7,3,2],
+            [7,5,1,3],
+            [5,4,0,1]
+        ],
+        convexity = 10);
+    polyhedron(
+        points = [
+            [width-wall_diff, near_pillar_width+wall_diff,       height+notch_height+epsilon],
+            [width-wall_diff, length-far_pillar_width-wall_diff, height+notch_height+epsilon],
+            [width-wall_diff, near_pillar_width+wall_diff,       -epsilon],
+            [width-wall_diff, length-far_pillar_width-wall_diff, -epsilon],
+            [width+wall_diff, near_pillar_width-wall_diff,       height+notch_height+epsilon],
+            [width+wall_diff, length-far_pillar_width+wall_diff, height+notch_height+epsilon],
+            [width+wall_diff, near_pillar_width-wall_diff,       -epsilon],
+            [width+wall_diff, length-far_pillar_width+wall_diff, -epsilon]
+        ],
+        faces = [
+            [1,0,2,3],
+            [4,5,7,6],
+            [0,4,6,2],
+            [6,7,3,2],
+            [7,5,1,3],
+            [5,4,0,1]
+        ],
+        convexity = 10);
+
+    // drill the bolt holes
+    for (a=[[outer_wall_thickness/2, near_pillar_width/2],
+            [outer_wall_thickness/2, length - far_pillar_width/2],
+            [width - outer_wall_thickness/2, near_pillar_width/2],
+            [width - outer_wall_thickness/2, length - far_pillar_width/2]]) {
+        translate([a[0], a[1], -epsilon]) {
+            cylinder(   h=height + notch_height + 2*epsilon,
+                        r=bolt_radius,
+                        center=false,
+                        $fn=360);
+        }
+    }
+
+    // cut the tray insert slots
+    // note: the tray will be slightly narrower to
+    // give a more comfortable fit. If it is too loose or too tight,
+    // adjust the tray.
+    for (a=[    outer_wall_thickness,
+                width - outer_wall_thickness]) {
+        translate([ a,
+                    -epsilon,
+                    floor_depth + tray_depth/2]) {
+            intersection() {
+                rotate([0, 45, 0]) {
+                    translate([-tray_depth/sqrt(2)/2, 0, -tray_depth/sqrt(2)/2]) {
+                        cube([  tray_depth/sqrt(2),
+                                length - back_wall_thickness + epsilon,
+                                tray_depth/sqrt(2)]);
+                    }
+                }
+                translate([-tray_depth/2+0.5, 0, -tray_depth/2]) {
+                    cube([  tray_depth-1,
+                            length - back_wall_thickness + epsilon,
+                            tray_depth]);
+                }
+            }
+        }
+    }
+}
diff --git a/rack.bracket/raspberry-pi-rack-tray.scad b/rack.bracket/raspberry-pi-rack-tray.scad
new file mode 100644
index 0000000..48d53b0
--- /dev/null
+++ b/rack.bracket/raspberry-pi-rack-tray.scad
@@ -0,0 +1,196 @@
+/* [Screw holes for attaching the Raspberry Pi 4] */
+
+// Make the screw holes this much bigger than the
+// actual screw for a more comfortable fit
+// (a bigger number here will make the screws fit looser)
+screw_hole_fudge = 0.15; // [0:0.05:0.5]
+
+/* [Tray width] */
+
+// Make the tray this much narrower on each side
+// for a more comfortable fit in the frame
+// (a bigger number here will make the fit looser)
+tray_insert_fudge = 0.25; // [0:0.05:0.75]
+
+/* [Hidden] */
+
+tray_width = 58;
+tray_length = 85;
+tray_depth = 5;
+tray_lip_overhang = 10;
+inner_wall_thickness = 5;
+spacer_depth = 3;
+spacer_outer_radius = 3;
+
+screw_radius = 1.25 + screw_hole_fudge;
+screw_head_radius = 3;
+screw_head_depth = 2;
+pcb_depth = 2;
+spacer_center_width = 49;
+spacer_center_length = 58;
+spacer_from_edge = (tray_width - spacer_center_width) / 2;
+
+sd_window_width = 40;
+floor_window_width = sd_window_width;
+floor_window_border = (tray_width - floor_window_width) / 2;
+floor_window_length = tray_length - floor_window_border*2 - inner_wall_thickness;
+
+epsilon = 0.001;
+
+difference() {
+    union() {
+        // the main tray
+        intersection() {
+            union() {
+                translate([tray_insert_fudge, 0, 0]) {
+                    cube([  tray_width - 2*tray_insert_fudge,
+                            tray_length + tray_lip_overhang,
+                            tray_depth]);
+                }
+                
+                difference() {
+                    // the outer part of the curved handle
+                    translate([ tray_width/2,
+                                -tray_length*0.5 + 7.5,
+                                0]) {
+                        cylinder(
+                            h=tray_depth + spacer_depth + pcb_depth,
+                            r=tray_length*1.5,
+                            center=false,
+                            $fn=360);
+                    }
+                    
+                    // cut away the inside to make it a shell
+                    translate([ tray_width/2,
+                                -tray_length*0.5 + 5.4,
+                                -epsilon]) {
+                        cylinder(
+                            h=tray_depth + spacer_depth + pcb_depth + 2*epsilon,
+                            r=tray_length*1.5,
+                            center=false,
+                            $fn=360);
+                    }
+                    translate([ tray_width,
+                                -tray_length,
+                                -epsilon]) {
+                        cube([  2*tray_width,
+                                3*tray_length,
+                                tray_depth + spacer_depth + pcb_depth + 2*epsilon]);
+                    }
+                    translate([ -2*tray_width,
+                                -tray_length,
+                                -epsilon]) {
+                        cube([  2*tray_width,
+                                3*tray_length,
+                                tray_depth + spacer_depth + pcb_depth + 2*epsilon]);
+                    }
+                }
+                
+                // reinforce the curved handle
+                translate([epsilon, tray_length, tray_depth]) {
+                    rotate([-75, 0, 0]) {
+                        cube([tray_width - 2*epsilon, 2*sqrt(2), 6]);
+                    }
+                }
+                
+            }
+            
+            // cut away the ears of the tray
+            // where they jut through the curved handle
+            translate([ tray_width/2,
+                        -tray_length*0.5 + 7.5,
+                        0]) {
+                cylinder(
+                    h=tray_depth + spacer_depth + pcb_depth,
+                    r=tray_length*1.5,
+                    center=false,
+                    $fn=360);
+            }
+        }
+        
+        // place the 4 spacers
+        for (a=[    [spacer_from_edge,
+                        spacer_from_edge],
+                    [spacer_from_edge + spacer_center_width,
+                        spacer_from_edge],
+                    [spacer_from_edge,
+                        spacer_from_edge + spacer_center_length],
+                    [spacer_from_edge + spacer_center_width,
+                        spacer_from_edge + spacer_center_length]]) {
+            translate([a[0], a[1], tray_depth-epsilon]) {
+                // place the spacer
+                cylinder(
+                    h=spacer_depth + epsilon,
+                    r=spacer_outer_radius,
+                    center=false,
+                    $fn=360);
+
+                // place a small cone around it
+                cylinder(
+                    h=2 + epsilon,
+                    r1=spacer_outer_radius + 1,
+                    r2=spacer_outer_radius,
+                    center=false,
+                    $fn=360);
+            }
+        }
+
+        // the tray insert edge tabs
+        for (a=[    tray_insert_fudge,
+                    tray_width - tray_insert_fudge]) {
+            translate([ a,
+                        0,
+                        tray_depth/2]) {
+                intersection() {
+                    rotate([0, 45, 0]) {
+                        translate([-tray_depth/sqrt(2)/2, 0, -tray_depth/sqrt(2)/2]) {
+                            cube([  tray_depth/sqrt(2),
+                                    tray_length,
+                                    tray_depth/sqrt(2)]);
+                        }
+                    }
+                    translate([-tray_depth/2+0.5, 0, -tray_depth/2]) {
+                        cube([  tray_depth-1,
+                                tray_length,
+                                tray_depth]);
+                    }
+                }
+            }
+        }
+    }
+
+    // punch a hole in the bottom
+    translate([ floor_window_border,
+                floor_window_border,
+                -epsilon]) {
+        cube([  floor_window_width,
+                floor_window_length,
+                tray_depth + 2*epsilon]);
+    }
+    
+    // drill the 4 screw holes
+    for (a=[    [spacer_from_edge,
+                    spacer_from_edge],
+                [spacer_from_edge + spacer_center_width,
+                    spacer_from_edge],
+                [spacer_from_edge,
+                    spacer_from_edge + spacer_center_length],
+                [spacer_from_edge + spacer_center_width,
+                    spacer_from_edge + spacer_center_length]]) {
+        translate([a[0], a[1], -epsilon]) {
+            // drill the main screw hole
+            cylinder(
+                h=tray_depth + spacer_depth + 2*epsilon,
+                r=screw_radius,
+                center=false,
+                $fn=360);
+
+            // drill a recessed hole for the screw head
+            cylinder(
+                h=screw_head_depth + epsilon,
+                r=screw_head_radius,
+                center=false,
+                $fn=360);
+        }
+    }
+}
\ No newline at end of file