strap-bar

from The Century Dictionary.

• noun The bar which carries the belt-fork on a counter-shaft combination or similar place, where a belt is to be shifted from a fast to a loose pulley on a shaft. The bar is guided by slots in brackets projecting from the hangers, and may be moved in the direction of its length by cords over pulleys or by a lever.
• noun One of the bars connecting the first transverse bar of a cupel-hearth with the frame or test-ring.