Bolts and screws are externally threaded male fasteners that are used with female-threaded fasteners or holes. Bolts are normally inserted through the materials being connected and held together with a nut or other female-threaded fastener. They are generally larger than screws and used for high-load applications. Screws are normally driven into components or surfaces and engage with female threads that are cut into the fastening surface. Drilling and tapping screws do not require a pre-drilled hole to be fastened to a surface or component while non-tapping screws require a threaded pilot hole. Socket head cap screws are used in applications where a normal bolt or screw may be too weak or take up too much space. Specialty shoulder screws and set screws are used in mechanical assembly to allow parts to rotate or hold rotating components together.