The standard sleeper sofa looks like a regular couch; it has three cushions with arms on each end. Underneath the cushions and inside the base of the sofa is a folding bed frame with springs. A mattress fits on top of this frame. The bed frame is pulled up and out of the sofa partially folded, and then the bottom section of the bed is unfolded. Traditionally, these types of sofa sleepers were heavy, but more recent versions are lighter.
A sectional sleeper sofa is similar to the standard sleeper sofa. A sectional sofa has at least two sections and can have more than that, depending on the space available for the sofa. The sections meet at a corner so that the sofa seats run at right angles to each other. The folding bed frame is housed in one section of the sofa and lines up with the other arm to form a larger sleeping space.
A convertible sofa does not have a folding bed frame to hide in its base, so it can be more modern and versatile in appearance. Convertible sofas feature reclining backs that flatten out into a bed. Several methods are available for flattening the back. The European method is known as click-clack because the sofa back ratchets back until it is flat. The split-back sofa can recline into a lounger or into a bed because the back can fold in two. The extending arms sofa has pieces that fold on either end that allow the arm rests to be adjusted to different heights or flattened completely when used as a bed.
The futon is another type of sofa that can turn into a sleeper. A futon is made up of a basic frame, generally made of metal or wood that can lay flat to become a bed or be folded in half to form a couch. Metal is the most common material that futon frames are made of because it is lighter and less expensive. Futon mattresses are flexible and are used both as the sofa cushions and as the bed mattress.