Overhead conveyors are type of conveyor. It consists of a continuous chain running beneath a continuous, stationary, flanged rail. Individual carriers spaced equidistant along the length of the conveyor are suspended from the chain. The chain pulls the carriers. Vertical support is derived from the fact that the carriers are also connected to a small trolley with wheels that roll cross sections, trolleys and carriers. A few common carriers include a tray, platform or simple hook. A less common alternative to the chain drive is a worm drive.