$fn = 64;

// A patterned side
module side() {
  difference() {
    cylinder(d=20, h=3);
    union() {
      translate([12.5, 0, 2.01]) difference() {
        cylinder(d=20, h=1);
        cylinder(d=18, h=1);
      }
      translate([-12.5, 0, 2.01]) difference() {
        cylinder(d=20, h=1);
        cylinder(d=18, h=1);
      }
    }
  }
}

union() {
  translate([0, 0, 4.5]) side();
  translate([-5, -5, 3]) cube([10, 10, 1.5]);
  translate([0, 0, 3]) rotate([0, 180, 0]) side();
}