Double end, 1 1/2 side, double bottom construction. Medium duty for use with or without shelving. FastFold quick and easy assembly. Deep locking lift-off lid stays in place for secure file storage. Rolled edges add strength and prevent paper cuts. Box Type: FastFold; Material(s): 1 Ply Side;2 Ply Bottom;2 Ply End; Strength: Medium-Duty.