small_dist = 0.1;

depth = 20;
width = 340;
height = 152;
thickness = 3;
tab_width = 20;
tab_hole_r = 2.5;

mount(depth, width, height, thickness);

module mount(depth, width, height, thickness){
    union(){
        tab(depth, tab_width, thickness, tab_hole_r);
        translate([(width+tab_width)/2, 0, -height])
        U(width, height, depth, thickness);
        translate([width+tab_width, 0, 0])
        tab(depth, tab_width, thickness, tab_hole_r);
    }
}

module tab(depth, width, thickness, hole_r) {
    difference(){
        cube([width, depth, thickness], center=true);
        cylinder(r=hole_r, h=thickness+small_dist, center=true);
    }
}

module U(width, height, depth, thickness){
    union(){
        cube([width+2*thickness, depth, thickness], center=true);
        translate([-(width+thickness)/2, 0, height/2])
        cube([thickness, depth, height], center=true);
        translate([(width+thickness)/2, 0, height/2])
        cube([thickness, depth, height], center=true);
    }
}