In the craft of woodturning

Woodturning

Woodturning is a form of woodworking that is used to create wooden objects on a lathe . Woodturning differs from most other forms of woodworking in that the wood is moving while a stationary tool is used to cut and shape it...

, a banjo is a common term for a fixture on the wood lathe, mounted on the lathe's bed, for holding the toolrest. It allows for adjustment of the toolrest in various positions, by the lathe operator, making it possible to hold the turning tool in the most convenient position for removing material from the spinning wood.
The chosen position of the fixture can be locked in place on the lathe's bed in various ways, the most common method being a lever at the forward end of the fixture which acts upon an eccentric

Eccentric (mechanism)

In mechanical engineering, an eccentric is a circular disk solidly fixed to a rotating axle with its centre offset from that of the axle ....

shaft with an attached clamp to secure the fixture to the lathe's bed.