$fn=33;

height=40;
hwidth=40;
thickness=5;

vthickness=20;
vwidth=40.3;
vheight=80;

M3HoleDiam=3.4;

holedistance=10;

horizontalcenterholes=true;

difference() {
    frame();
    holes();
}

module frame(){
    // left tile 
    cube([hwidth,thickness,height]);
    translate([0,thickness,0]) sidetriangle();
    translate([0,thickness,height - thickness]) sidetriangle();
    
    // left to back tile
    translate([hwidth,0,0]) cube([thickness, vthickness, height]);
    
    // left triangle
    translate([hwidth,thickness,height]) rotate([90, 0, 90]) middletriangle();

    // covers upper edge of above
    translate([hwidth, vthickness, 0]) cube([vwidth + thickness * 2, thickness, vheight]);

// right to back tile
    translate([hwidth + vwidth + thickness,0,0]) cube([thickness, vthickness, height]);
    
    // right triangle
        translate([hwidth + vwidth + thickness,thickness,height]) rotate([90, 0, 90]) middletriangle();

// right tile
    translate([hwidth + vwidth + thickness * 2, 0, 0]) cube([hwidth,thickness,height]);
    
        translate([hwidth * 2 + vwidth + thickness * 2,thickness,thickness]) rotate([0, 180,0 ]) sidetriangle();
        translate([hwidth * 2 + vwidth + thickness * 2,thickness,height]) rotate([0, 180,0 ]) sidetriangle();
    
}

module middletriangle(){
    linear_extrude(thickness) polygon([[0,0], [vthickness-thickness, 0], [vthickness-thickness, vheight-height]]);
}

module sidetriangle() {
    linear_extrude(5) polygon([[0,0], [hwidth, 0], [hwidth, vthickness]]);
}

module holes() {
    // left holes
    leftholes();
    
    // right holes
    translate([hwidth + vwidth + thickness * 2,0,0]) leftholes();
    
    // center holes
    translate([hwidth + thickness,vthickness,0]) centerholes();
}

module leftholes(){
    translate([holedistance, 0, holedistance]) XM3Hole();
    translate([hwidth - holedistance, 0, holedistance]) XM3Hole();
    translate([holedistance, 0, height - holedistance]) XM3Hole();
    translate([hwidth - holedistance, 0, height - holedistance]) XM3Hole();
}

module centerholes() {
    translate([holedistance, 0, holedistance]) XM3Hole();
    translate([vwidth - holedistance, 0, holedistance]) XM3Hole();
    translate([holedistance, 0, vheight - holedistance]) XM3Hole();
    translate([vwidth - holedistance, 0, vheight - holedistance]) XM3Hole();
    
    if(horizontalcenterholes){
    // center holes
    translate([vwidth - holedistance, 0, vheight / 2]) XM3Hole();
    translate([holedistance, 0, vheight / 2]) XM3Hole();
    }
}

module XM3Hole() {
    rotate([270,0,0])cylinder(h=thickness, d=M3HoleDiam);
}