Medium-duty storage boxes with lids offer double-end, 1-1/2 side, double-bottom construction and medium-duty use with or without shelving. FastFold One Step Setup makes box assembly fast and easy. Deep, locking liftoff lid stays in place for secure file storage for your letter-size files. Smooth, rolled box edges add strength and help prevent paper cuts. Storage boxes are built for moderate use and high stacking needs. Stack up to five units high. Average amount of evenly distributed weight that can be safely stacked on top of box is 650 lb.