Next time you’re passing by a cliff and happen to see a precariously hanging tent with campers inside, don’t be alarmed, it’s just a portable ledge (portaledge):

Portaledges — or deployable hanging tents — might seem like a thrill-seeking activity (and it can be), but the idea has actually been around since the 1950s. During this time, rock climbers began to stay overnight on the mountains they were scaling and started looking for convenient niches in the mountain side to make their bed.

The first portaledges were used in Yosemite National Park and were non-collapsible cots or hammocks. Climbers would sit on a Navy surplus canvas chair and rest their heads on their dangling rucksacks.