Sofa Bed Mattress

• The mattress located inside the sofa is one of the most important components of the piece. Without a mattress, the couch is simply another couch. Sofa bed mattresses are typically thin and lightweight because the mattresses fold inside the couches. Older mattresses typically have a tri-fold design as the mattress folds three times for a proper fit inside the couch. Newer designs fold the mattresses in different ways.
  
  

Folding Mechanism

• A metal frame that fits inside the couch and attaches to both the bottom and sides of the piece is the folding mechanism. Thin strips of metal or wire run across the frame and provide a support system, similar to the way a box spring or foundation supports the mattress on your regular bed. The front of the frame has a handle or bent piece of metal that makes pulling the mattress out easier. You may also notice small legs on the base of the frame that fold into the couch. When you pull the mechanism out of the couch, the legs fold out and support the bed. Different types of couches use different mechanism shapes, including sectional couches, lounge chairs, love seats and full-size couches.
  
  

Couch Components

• Just as important as the parts of the sofa bed are the couch components because, without the couch, you just have a bed and frame. The couch has legs or a base that keeps the sofa stable and prevents it from tipping or falling over. The cushions on the couch make sitting more comfortable, and the couch has a backing. Metal or wood frames build the interior support system of the couch.
  
  

Exceptions

• The exception to sofa bed components are those furniture pieces sold as "click clack" or "convertible" sofas. The sofas lack a separate mattress or mechanism as the mattress is actually the base or seating portion of the couch. The back of the couch folds flat and creates a double or full-size bed.