The mechanism enables to unfold the surface to the cross – sleeping space, in both sofas or corners. The unfolding consists in uplifting the mechanism, while the backrest lifts up simultaneousely thanks to the additional mechanism used - PC 106-5, and moving it to the front onto the floor. The solution enables to unfold the function without touching the floor. Its adventage is also the same thickness and width of all matterasses. There is no limits in seat width, beacause the mechanism consists of 2 elements mounted to the sides of the furniture connected together just by the synchronising bar. The mechanism is constructed such way that the furniture unfolding and folding is supported by work of springs and synchronizing bars, which makes the function very easy in handling. The mechanism can substitute many old solutions for this kind of furniture.