Screws are used to hold two objects together or to fasten one object to the other. Some screws are designed to screw into a pre-threaded material (internal thread) such as a nut or a theaded hole while others screw directly into a surface while creating their own hole. Common screw head types include: round, flat, pan, oval, truss, and hex. Drive types include, phillips, slotted, torx, hex and socket. The most popular screws are: wood screws,stainless steel screws and machine screws.

Bolts can come fully or partially threaded depending on the bolt type. Common bolt head types include: hex, flange, button and flat heads. Various bolt drives include: socket, hex and square drives. The most popular bolts are:stainless steel bolts, grade 8 bolts, carriage bolts and hex bolts.

A bolt is an externally threaded fastener designed to  insert through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut. A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread, and of being tightened or released by torquing the head. An externally threaded fastener which is prevented from being turned during assembly and which can be tightened or released only by torquing a nut is a bolt, for example round head bolts, track bolts, plow bolts. An externally threaded fastener that has thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is a screw, for example wood screws, tapping screws.