Pieces of wood of various forms, though mostly round; they are for different purposes, as wheels on which the gun-carriages run.
♦ Trucks of the flag-staves or at the mast-head. Circular caps on the upper mast-heads; they are generally furnished with two or more small sheaves, through which the signal halliards are rove.
♦ Trucks of the parrels. Spherical pieces of wood, termed bull's-eyes, having a hole through them, in which is inserted the rope of the parrel. (See parrals.)
♦ Trucks for fair leaders, are similar to bull's-eyes, but are scored to fit the shrouds to which they are seized. The ropes are thus kept from getting jammed between the yards and the rigging; they are also useful, especially at night, as guides to particular ropes.