Agree with Peggie on Polypropylene. Lead is often used as a catalyst in manufacturing PVC. Agree with Charlie that acrylic can can be drilled with "standard" drills it does tend tip grab and chip and crack. Extra care needed. Agree with Charlie no flathead screws, however breaking the corner with a countersink (chamfering) is a good idea to prevent stress cracks from developing, especially in acrylic. My .02