Video:  Hahnel Brothers Co. employee building ductwork Assembling light gauge galvanized steel ductwork consists of taking the precut pieces and putting the appropriate locking details on each edge by running the edges through roll forming machines and then pounding the pieces together. One side edge is pounded into its receiver mate and secured in place by hammering over the excess edge of the receiver lock. The vise grips are used to keep the pieces from slipping during the hammering process.