How to Fix a Sagging Couch?

We fixed a sagging loveseat (small couch) by placing a sheet of plywood under the cushions. You have to be sure the edge of the wood rests on the wooden frame next to the cushions. It will have to be cut so that the wood does not poke out from under the cushions at the front. Sitting on this will feel very firm and you will have to stop the kids from jumping the couch after you place the wood under the cushions!