BOTHY BAG

 

British style weather shelter

Bothy Bags are little known in the US. Well known in Britain.
A bothy bag is basically a simple waterproof nylon "box" with an open bottom and a draw-cord round the base. In use, the occupants become the structural elements, cinching up the draw cord a bit, sitting on the skirt which is formed inside, with their backs supporting the walls. The most common sizes are the two-man, and four-man (1.3lbs,$60)
As a piece of weather emergency gear a Bothy Bag has several advantages over a bivi-sack: primarily, the body heat of multiple occupants generates a surprisingly warm shelter. Climbers can recover their morale, sit out the night, or just eat lunch and chat. Also, no need to remove your crampons or clothing layers. One bothy bag certainly beats multiple bivy-sacks in most situations.
Link: moontrail.com/home.php?cat=300
also: http://www.youtube.com/watch?v=OpTS_WYwbIk