Many theaters of the Civil War were criss-crossed by rivers and streams not suitably bridged to accommodate the strategy of an army, or often had existing bridges destroyed by a retreating army. To combat this problem, among the leading troops of an advancing army, were the engineers and their bridging train of wagons.

To construct a bridge the pontonniers floated to position the first pontoon and then the second. Lashed across these were the balks; and on these were laid the chesses (planks) to form the treadway of the bridge. As more pontoons were floated downstream to position, the further balks and chesses completed the connection of both banks. To speed construction, whole sections could be made up by the bank, and floated down stream into position.

At the Battle of Fredericksburg great valor was displayed when attempting to bridge the Rappahannock River under heavy fire from Confederate sharpshooters on the far bank. Bridging was only completed after detachments crossed the river in pontoons to dislodge the enemy.