A typical lean-to. This one is on Black Pond in Keeseville Standard plan for an Adirondack lean-to or open camp designed by New York State Conservation Department, Bureau of Camps & Trails, March 1957 A lean-to is a free-standing structure of three walls with a sloping roof, usually used for camping, and located near a lake or pond, or in the mountains. The open side is sheltered away from the prevailing winds and rains. It is usually a rough structure made of logs or unfinished wood.

"An Open camp in the Adirondacks"
Detroit Publishing, c. 1903
See guide Joe Hackett's Adirondack Gadabout column in the Adirondack Daily Enterprise of December 8, 2012, for more on lean-tos.