Phillips, Truss, Self Tapping/Sheet Metal Screws, Type A. Type A thread for self starting in thin (.015 - .050 inch thick) metal or resin-filled plywood. Truss head screws are weaker than pan or round heads but preferred in applications where minimal clearance exists above the head. Modified truss heads offer low clearance and an extra large bearing surface. Commonly used to attach metal lathe to metal studs.