Got shelves that bend in the middle? Do they sag due to years of supporting heavy weight? Learn how to bring shelves up for level support of books (and other stuff)!
One of the best and easiest solutions is to clear off the shelf, remove it, turn it over, and let the weight of its contents bear down in the opposite direction for a while. Doing this every so often will average the bow.
A more permanent solution is to add a support along either the length of the back or front edge in the form of trim molding or one-by-two lumber.
For kitchen cabinets or bathroom lavatories, remove sagging shelves and draw a straight line across the back where the shelf edge should be. Drill a number of holes the same size as those used for the shelf support pegs on either side, then insert additional peg supports (purchased at any hardware store or home center.) Replace and reload your shelves, and presto up-o, they’ll be good as new. They’ll stay that way, too. When shelves sag, don’t get mad…be ‘supportive’ instead!