A truck is a wooden ball, disk, or bun-shaped cap at the top of a mast, with holes in it through which flag halyards are passed.
[citation needed] Without a masthead truck, water could easily seep into the circular growth rings of a wooden mast.
However, the grain in the truck is perpendicular to that of the mast, allowing the water to run off it.
[citation needed] Flagpoles often have a truck on top of them which often holds a decorative piece above, known as a finial, which is usually a ball.
They are usually made of solid metal, however a tradition in the United States is to sometimes put a razor, a penny, or a grain of rice inside.