Z Series Butt Hinges is one of the common door hinges that is found on doors and cabinets that consists of two rectangular leaves with knuckles in the middle, joined by a pin. These are available in four types: plain bearing, ball bearing , spring-loaded, and rising. Z Series Butt Hinges is a good choice for heavy doors that are permanently lubricated to make closing and opening heavy doors smoother and ensure the hinges can stand up to frequent use with a heavy door.