Fasteners come in many different forms. Bolts and nuts are used for joining wood in heavy wood construction (roof trusses and rafters), fastening heavy wood structures to iron constructions, a connection of parts on iron construction. Woodscrews are used for joining wood, fastening ironwork to wood, fastening hardware (hinges, locks, catches) to wood. A screw is a metal fastener with a spiral thread cut in. Carriage Bolts, Hex Head Bolts, Machine Screws, Shoulder Bolts, Socket Cap Screws, Socket Set "Grub" Screws, Square Head Bolts, Deck Screws, Hex Lag Screws, Self-Drilling Screws, Sheet Metal Screws, Wood Screws, Cap Nuts, Castle Nuts, Coupling Nuts, Flange Serrated Nuts, Hex Finish Nuts, Hex Jam Nuts, Heavy Hex Nuts, Hex Machine Nuts, Hex Machine Nuts Small Pattern, Keps-K Lock Nuts, Knurled Thumb Nuts, Nylon Hex Jam Nuts, Nylon Insert Lock Nuts, Prevailing Torque Lock Nuts (Stover), Slotted Hex Nuts, Square Nuts, Structural Heavy Hex Nuts, T-Nuts, Break Away or Shear Nuts, Tri-Groove Nuts, Wing Nuts.