When you camp, a tent often has two skins. The inner tent is where you sleep. Over the top you stretch a second sheet of waterproof cloth, held out on poles and pegs so rain hits that sheet and runs off. That outer sheet is the flysheet. There is usually a little air gap between the two layers; that gap matters. If the wet flysheet lies against the inner tent, water can creep through, and you wake up damp. British campers say flysheet (sometimes fly sheet, two words). In American shops you will more often see rainfly or rain fly. Same job. Though actually, some people also say just “the fly” for that outer cloth. The fly here is not the insect. In camping English, a fly is an extra cloth cover. The groundsheet is a different thing: that one goes under you, on the floor. Flysheet over; groundsheet under.

外帳