Bivouac shelter

[3] The word bivouac is French and ultimately derives from an 18th-century Swiss German usage of Beiwacht (bei by, Wacht watch or patrol).

[2] Artificial bivouacs can be constructed using a variety of available materials from corrugated iron sheeting or plywood, to groundsheets or a purpose-made basha.

Generally a basha is made of reinforced nylon with eyelets and loops or tabs located along all four sides of the sheet and sometimes across the two central lines of symmetry.

A bivouac sack will usually have a thin waterproof fabric shell that is designed to slip over a sleeping bag, providing an additional 5 to 10 °C of insulation and forming an effective barrier against wind chill and rain.

Fully zipping up a bivouac sack is poor practice, both from the obvious risk of hypoxia and the dramatically increased levels of condensation that will form inside the bag.

[citation needed] In the German region of Saxon Switzerland in the Elbe Sandstone Mountains, climbers refer to overnighting in the open air as Boofen (pronounced "bo-fen").

[7] The spot selected for overnight stays usually comprises an overhang in the sandstone rock or a cave, the so-called Boofe ("bo-fe").

In the national park itself, Boofen is only permitted at designated sites and only in connection with climbing, although in this case lighting fires is absolutely forbidden.