$fn = 500;

//cylinder(h=10, d=11);
// 4.5 thick under screw
// 12 diameter screw head hole (~10.8 screw head)

e = 0.02;
w = 50.8;

difference() {
    union() {
        hull() {
            for (x=[0, 15], y=[0, w - 1])
            translate([x, y, 0]) {
                translate([0.5, 0.5, 0])
                cylinder(h=1, d=1);
                
                translate([0.5, 0.5, 1.0])
                sphere(d=1);
            }
            
            for (x=[0, 15])
            translate([x, 0, 0]) {
                translate([0.5, w / 2, 15])
                rotate([0, 90, 0])
                rotate_extrude()
                translate([7, 0, 0])
                circle(d=1);
             }
        }

        for (x=[-0.25, 11.25], y=[12.7 - (6.5 / 2), w - 12.7 - (6.5 / 2)]) {
            translate([x, y, 0])
            rotate([-90, 0, 0])
            intersection() {
                translate([0.5, -0.5, 0])
                hull()
                for (p=[[0, 0], [1.5, 1.5], [2.5, 1.5], [4, 0]]) {
                    translate([p[0], p[1], 0])
                    cylinder(h=6.5, d=1);
                }
                
                cube([10, 10, 10]);
            }
        }
    }
    
    translate([-e, w / 2, 15])
    rotate([0, 90, 0])
    cylinder(h=10, d1=8.2, d2=8.1);
    
    for (y=[12.7, w - 12.7])
    translate([0, y, 0]) {
        translate([8, 0, -e]) {
            cylinder(h=20, d=6.8);
            
            translate([0, 0, 4])
            cylinder(h=20, d=12);
        }
    }
}