Even though you don't see the sofa's structure, it forms the basis of how comfortable the sofa is for the user. A comfortable sofa has a frame designed in such a way that it's easy to get up and down from the seated position. The frame needs to be sturdy enough to support the weight of several people. Look for sofa frames constructed of hardwood, such as kiln-dried ash, oak or beech. Examine the legs of the sofa. They should either be part of the frame itself or attached with dowels or screws. If you raise one of the front corners of a sofa, the other front leg should come off the floor as well, if the sofa has a solid structure. If the other leg doesn't rise from the floor, the sofa is structurally weak and may not be comfortable over time