what keeps astronauts in place when sleeping in zero gravity

Astronauts sleep in space by strapping their bodies loosely so that they do not float around. They use small sleeping compartments and sleeping bags to sleep in any orientation since there is no "up" or "down" in zero gravity. The sleeping bags are strapped to the wall, and astronauts can sleep anywhere facing any direction. Eye masks and earplugs are also available for the astronauts who are unable to sleep due to the noise from air conditioning and other machines. The sleeping cycle of astronauts in space allocates eight hours for sleeping, but they usually sleep for around six hours since they often work long hours or spend their time enjoying the view of the outside from the shuttles window. Astronauts have reported having nightmares, dreams, and snoring while sleeping in space. The quality and quantity of sleep of astronauts in space are markedly reduced than while on Earth. Research suggests that the use of sleep-inducing medication could be indicative of poor sleep due to disturbances. Astronauts have dark, quiet, and private crew quarters on the space station conducive to good sleep. They also use special restraints to keep them from floating through the space station while asleep.