seg = 360;
outer = 12;
height = 6;
rad = 1;
dist = 4;

rotate_extrude($fn = seg)
difference()
{
	square([outer, height]);
	translate([0, height - 3.5, 0])
	{
		square([10.5, 3.5]);
	}

	translate([outer, height - dist, 0])
	{
		circle(rad, $fn = seg);
	}
}