BSW - Combination Slot/Phillips - Zinc Plated - Mushroom Head - Roofing Bolts are a general purpose designed mushroom headed bolt with a combination phillips and slot drive complete with hex nuts, These bolts are ideal for roofing, guttering and many other applications. Supacheap Bolts currently stock 3/16", 1/4" and 5/16" diameters up to 3" in length for certain diameters.