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; File Size Format: Letter.