A shed is typically a simple, single-story roofed structure in a back garden or on an allotment that is used for storage, hobbies, or as a workshop. Sheds vary considerably in the complexity of their construction and their size, from small open-sided tin-roofed structures to large wood-framed sheds with shingled roofs, windows, and electrical outlets. Sheds used on farms or in industry can be large structures. The main types of shed construction are metal sheathing over a metal frame, plastic sheathing and frame, all-wood construction (the roof may be asphalt shingled or sheathed in tin), and vinyl-sided sheds built over a wooden frame.