slot hole

slot_hole.scad

module slot_hole(
        width = 5,  //width/dia at ends
        length = 20,  //length
        thickness = 5  //thickness
        )
{
    hull() {
    translate([-length/2+width/2, 0, 0]) polyhole(h=thickness, d=width);
    translate([length/2-width/2, 0, 0]) polyhole(h=thickness, d=width);
    }
}