A couch bed is a piece of furniture that can be converted from a couch into a sleeping surface. The most common type of couch bed is the sleeper sofa, or hide-a-bed, which features a fold-out mattress that can be stowed beneath the couch cushions when not in use. Other types of couches that can be converted into a bed include futons and folding couches that allow the seat back to fold down, providing an essentially flat surface on which one can sleep without having to pull a mattress out.
The pullout couch bed features a mattress mounted to a metal frame that can fold in on itself. The metal frame is hinged in several places to allow the folding, and when it is pulled out, legs fold down to support the far end of the frame. The mattress for such a bed is generally much thinner than a typical bed mattress, as it would not be allowed to fold otherwise. These types of couches tend to be significantly heavier than other models, since the metal frame of the bed portion can add a fair amount of weight.
A futon is a type of couch that folds down flat by reclining the seat back of the couch. This design is based on traditional Japanese beds, but they function differently. The mattress itself is similar to traditional styles, though it is likely to be much thicker. Many people prefer futons over the pullout couch bed because the mattress is thicker and more comfortable, as well as easier to set up and take down. Futons are often mounted on wooden or metal frames that are hinged at the center to allow reclining.
More modern versions of the couch bed tend to mimic the function of the futon, but with a more aesthetically pleasing design. Some couch beds can be designed to look just like any other couch, with a variety of materials, designs, and colors, but fold down in a similar fashion to a futon. Sometimes the couch includes throw pillows that can be used as sleeping pillows when the couch is folded down.
Some specially designed couch bed models are made for RVs that have limited space inside. The couch can be folded down flat to create a sleeping surface, and when no one is sleeping on it, the couch can be folded back up to provide a sitting surface for living, eating meals, relaxing, or sitting while the vehicle is in motion.