parts of machine tools, usually bearing surfaces, that by interacting with the surfaces of the parts that are in contact provide precise motion of moving parts (such as machine tables or rests) along a predetermined straight or circular path. A distinction is made between sliding and rolling guides.

Guides must be precisely machined and must have high wear resistance, rigidity, and vibration resistance. The durability of guides is ensured by the hardness and low degree of roughness of the working surfaces, by reliable lubrication, and by meticulous care during use. Guides are usually equipped with devices for periodic adjustments of the clearances between contact surfaces and for periodic compensation for wear. Components that perform analogous functions in other machines, mechanisms, and instruments are also called guides.