Pontoon bridge, is made of pontoons, slipped into the water, and placed about five or six feet asunder; each fastened with an anchor, when the river has a strong current, or to a strong rope that goes across the river, running through the rings of the pontoons. Each boat has an anchor, cable, baulks, and chesses. The baulks are about 5 or 6 inches square, and 21 feet long. The chesses are boards joined together by wooden bars, about 3 feet broad and 21 feet long. The baulks are laid across the pontoons at some distance from one another, and the chesses upon them joined close; which makes a bridge, in a very short time, capable of supporting any weight.
Source: Duane, William: A Military Dictionary (Philadelphia, 1810)