group() {
	difference();
	difference();
	difference() {
		cube(size = [10, 10, 10], center = true);
		cylinder($fn = 0, $fa = 12, $fs = 2, h = 20, r1 = 4, r2 = 4, center = true);
	}
	multmatrix([[1, 0, 0, 12], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		difference() {
			cube(size = [10, 10, 10], center = true);
			cylinder($fn = 0, $fa = 12, $fs = 2, h = 10.5, r1 = 4, r2 = 4, center = true);
		}
	}
	multmatrix([[1, 0, 0, 0], [0, 1, 0, 12], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		difference() {
			cube(size = [10, 10, 10], center = true);
			cylinder($fn = 0, $fa = 12, $fs = 2, h = 11, r1 = 4, r2 = 4, center = true);
			multmatrix([[0, 0, 1, 0], [0, 1, 0, 0], [-1, 0, 0, 0], [0, 0, 0, 1]]) {
				cylinder($fn = 0, $fa = 12, $fs = 2, h = 11, r1 = 4, r2 = 4, center = true);
			}
		}
	}
	multmatrix([[1, 0, 0, 12], [0, 1, 0, 12], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		difference() {
			cube(size = [10, 10, 10], center = true);
			multmatrix([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 7.01], [0, 0, 0, 1]]) {
				cylinder($fn = 0, $fa = 12, $fs = 2, h = 4, r1 = 4, r2 = 4, center = true);
			}
		}
	}
	multmatrix([[1, 0, 0, 24], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		difference() {
			cube(size = [10, 10, 10], center = true);
			multmatrix([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 6.99], [0, 0, 0, 1]]) {
				cylinder($fn = 0, $fa = 12, $fs = 2, h = 4, r1 = 4, r2 = 4, center = true);
			}
		}
	}
	multmatrix([[1, 0, 0, 24], [0, 1, 0, 12], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		difference() {
			cube(size = [0, 10, 10], center = true);
			cylinder($fn = 0, $fa = 12, $fs = 2, h = 20, r1 = 4, r2 = 4, center = true);
		}
	}
}