4×3/8 #3 hd phillips truss high low screw fully threaded zinc bake. High-low thread for use in plastic, nylon, wood or other low-density materials. Thread design reduces driving torques, enhances resistance to thread stripping, improves pullout strength and lessens the risk of cracking the work piece. 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.