Bivouac shelter
A bivouac shelter or bivvy (alternately bivy, bivi, bivvi) is any of a variety of improvised camp site or shelter that is usually of a temporary nature, used especially by soldiers or people engaged in backpacking, bikepacking, scouting or mountain climbing. It may often refer to sleeping in the open with a bivouac sack, but it may also refer to a shelter constructed of natural materials like a structure of branches to form a frame, which is then covered with leaves, ferns and similar material for waterproofing and duff (leaf litter) for insulation.