$fn=24;
length = 60;

module screwHole() {
  color("blue") union() {
    translate([2.1, 5.1, 0]) cylinder(r = 2.1, h = 6);
    translate([2.1, 2.1, 0]) cylinder(r = 2.1, h = 6);
    translate([0, 2.1, 0]) cube([4.2, 3, 6]);
  }
}

difference() {
  union() {
    // channel
    cube([30, 13, length + 10]);

    // angled support
    translate([16, 9, -8]) rotate([0, -17, 0]) cube([30, 4, length + 10]);

    // base
    cube([50, 32, 4]);
  }

  union() {
    // bottom flush-cut
    translate([-10, -10, -20]) cube([60, 40, 20]);

    // X-side flush-cut
    translate([-8, -2, -length * 0.05]) cube([8, 20, length * 1.1]);

    // channel interior
    translate([3, 3, 4]) cube([23, 9, length]);

    // channel side cutaway
    translate([4, 8, 4]) cube([20, 9, length]);

    // screw holes
    translate([4.2, 32 - 7.2 - 4, -1]) screwHole();
    translate([50 - 8.4, 32 - 7.2 - 4, -1]) screwHole();
    translate([25 + 4.2, 32 - 5.7 - 4, -1]) rotate([0, 0, 90]) screwHole();

    // top flush-cut
    color("red") translate([-10, -8, length]) cube([60, 40, length / 2]);
  }
}