Early Lean-to Construction
In 1939 the Appalachian Trail Conference issued guidelines to its member clubs regarding the construction of shelters (then called lean-tos) along the Appalachian Trail. The goal, as stated in this document, was to place shelters approximately 10 miles apart:
Such spacing avoids undue exertion for travelers carrying heavy packs and yet permits "skipping" a lean-to by more strenuously inclined traveler's for their day's journey.
The design of the lean-tos was to follow the general design of the Adirondack shelter: three-walled, with a steeply sloping roof, and a stone fireplace at the front that would radiate heat into the structure.