Tuesday Tool Tip: How do I know which type of Kreg screw to use when joining 1/2"-thick material? // Yesterday we had a customer express confusion regarding our screw chart. He didn't know whether to use 3/4" or 1" Kreg screws when working with 1/2"-thick material. So, we've created a Tool Tip that explains the difference: If you're joining 1/2"-thick material to 1/2"-thick material, use a 3/4" screw. If you're joining 1/2"-thick material to material that is thicker than 1/2", use a 1" screw.