A Bailey bridge or mechano bridge is a prefabricated portable bridge designed for military use. It is used to save "Light (engineering)" lights of up to 60 meters by assembling elements of about 3 meters in length, easily transportable by truck. Its assembly does not require special tools or heavy equipment, it takes just a few hours and can be carried out even under enemy fire. This bridge was designed as a solution to the increased weight of the new battle tanks that were being developed in the early phases of the war. This invention is considered one of the best examples of military engineering during World War II.

The Bailey Bridge was presented to his superiors by Donald Bailey&action=edit&redlink=1 "Donald Bailey (civil engineer) (not yet redacted)"), who worked in the British Army War Office during the Second World War. Production began in July 1941, entering service in December of that same year. In total, nearly 490,000 tons of Bailey bridges were manufactured during the war, adding up to a total of 320 kilometers in length of fixed bridges and about 64 km of floating bridges. Its characteristics allowed it to be used in all theaters of operations, although its use stands out in the Allied invasion of Italy and for the northeastern European campaign that occurred after the Normandy landings, thanks mainly to the fact that the United States acquired a license for its production.

Donald Bailey was knighted for this contribution.