Ajax (crane barge) is a type of boat that carries a crane. Cranes are pieces of heavy machinery used for lifting and moving things like cars, large pipes, and other heavy equipment. Cranes on ajax barges are often used for construction, like building bridges or towers. The crane has a big arm with a big metal hook on the end that can lift heavy things up and move them around. The barge itself has a flat bottom so that it can travel on water and can go wherever it needs to.