Gantry traveler

A framework of two or three bents or gallows frames, braced longitudinally and carried on a track supported on falsework and placed outside of the  trusses. The traveler clears the span at all points and can be rolled back and forth as needed. It carries a number of blocks and  tackles which are operated by a hoisting engine placed on a platform near the base. It is used in erection for hoisting and placing the members of a truss.