Do you need a separated mattress or not?

Do you need a separated sofa sleeper mattress?

• If yes,then you will choose from folded catagories like Bi-fold,Tri-fold,and Revolving sofa bed mechanisms.If not you will choose from no mattress categories like click clack hinges,drawer-out mechanism,pull out pop up mechanism and sliding sofa bed mechanism.
• If you choose from folded catagories, the the mounting depth is the key to figure out right folded sofa bed mechanism.
• If you choose from no mattress catagories,there are many choice for your design,such as full length of sofa bed or just side sleeper,zero wall function or none-zero wall function,futon sofa or real sofa bed etc.