A steel frame with steel wheels on a horizontal shaft, which houses parallel inline sheaves on a shaft with bearings which are lubricated with grease system. It is suspended in the derrick or mast with wire rope from the crown block. It is used to hang tools and equipment such as elevators, bails, and rod hooks.
On a workover rig, the travelling block is used to hold the power swivel and to run drillpipe or casing. On a pulling unit, it is used to run tubing or rods in or out of the well.