Bolts are mechanical fasteners, usually used with nuts, for connecting two or more parts. Bolted joints can be readily disassembled and reassembled; hence bolts or screw fasteners are used more than other types of mechanical fastener. A bolt consists of a head and a cylindrical body with screw threads along a portion of its length. Nuts have internal (or female) threads to match those of the bolt. Washers are often used to prevent loosening and crushing.