Conveyors are today widely recognized as the basic tool of mass production. The advantages of rapid mechanical materials handling need no arguing, particularly in the construction industry where the movement of materials presents so many perplexing problems. But the building site is not an enclosed, highly organized factory operating on repetitive jobs. Every site, however great the degree of planning that has prevailed, demands high standards of individual craftsmanship, freedom for personal initiative, and above all, flexibility to meet a thousand and one possible contingencies. Chicago's Marina City project has provided an excellent opportunity to demonstrate the convenience and economy of handling and placing concrete with lightweight conveyor flights so engineered that they can be used individually or readily assembled to create a conveyor system. The 30 foot long flights used extensively on the Marina City job weighed only 500 pounds each and the sections in any desired number and pattern may be connected together in a single electrical circuit with a common set of controls, so that when one flight stops for any reason all other flights are also stopped.