Pardon the question, but do your drawer bottoms sag? It's a common malady that strikes furniture drawers, especially wide ones with bottoms made of thin hardboard or plywood.
Here's the problem: The bottom fits into grooves cut in the drawer sides, front, and back. Over time, it begins to sag under the weight of the contents until it pops out of the groove milled in the drawer back. If it's not repaired quickly, the bottom will fall completely out, possibly damaging the drawer.
Start by squeezing some carpenter's glue into the groove in the drawer back. Push the drawer bottom into the groove and wipe off any excess glue. Cut a small block of solid wood or plywood to 3/8 inch thick X 2 inches wide X 4 inches long and glue it to the underside of the drawer bottom. Allow the glue to cure overnight.
Next, flip the drawer right-side up and fasten a 1 ½ X 1 ½-inch metal corner brace to the rear center of the drawer. Drive two screws into the drawer back and two down through the drawer bottom and into the wood support block. The brace effectively locks the drawer bottom in place and keeps it from coming out of the groove.
This technique can also be used to repair a sagging bottom that pops out of the groove in the drawer front or side.