Bottom's-up solution for sliding shelves
Turn one of your shelf supports upside down and cut a saw kerf in the shelf that will accept the angled brace on the bottom of the support. Slip the kerf over the inverted brace and the shelf will stay put. To avoid overloading the inverted shelf support, use these only on shelves that are lightly weighted.
—Alan Wolke, Phillipsburg, N.J.