There are many different mechanisms of transformation of furniture (over 15), but the most commonly used are: "French" clamshell, "book" or "click-klyak", "accordion", "roll-out" and "Dolphin." "French" clamshell. The most common mechanism (especially in foreign models, furniture). Upholstered furniture by using this mechanism can be any, the most fantastic design, as in the classics, so and in modern dance. But this mechanism does not provide a niche for linen. It has four performance classes: economical, poluortopedichesky, orthopedic and "daily sleep." Economy. As a "bed" is used Polypropylene deck (similar to the Soviet camp bed with a quality material and fabric does not pop up and do not stretch the springs) or a metal grid (similar to the Soviet iron beds with a metal net, only higher quality) plus a thin foam mattress. Sleep on the couch so hard, but possible.
Poluortopedichesky class – a cloth placed a few extra blades. Slats are made of laminated veneer lumber, which is attached by pressing curved shape. Because of its shape and material (for the slats used veneer of birch or beech) lamella "works" like a flat spring. This, in principle, be achieved orthopedic effect. The best (but more expensive) are beech slats.
Orthopedic class. The mechanism has 12-14 transverse lamellae. In his suite as part of a foam mattress (9 cm). Typically, the mattress is used standard (and cheapest) brand foam (ST-2534). If we talk about what should be (theoretically) your mattress – it must be of high density foam, and stiffness.