Designates a spot on the ground where people should sleep. Not comfortable.
A sleeping spot allows colonists or prisoners to rest on the floor. Handy for housing individuals until you are able of building them a bed or a room of their own, consider doing the latter as soon as possible.
A sleeping spot is extremely useful to save the life of a colonist that just have been incapacitated in a firefight. Simply place the sleeping slot close to where they have fallen, and assign it for medical use.