I've made about 25 drawers all with wood slides. Tried my first set of metal slides on a 39" x 6" drawer for a blanket chest. What a disaster. I realized the drawer box is not quite perfectly square....the rear tapers by a 1/16" or so. After futzing with a hand planer for 2+ hours today, I've decided to scrap the drawer and make a new one that uses the wood slide (which is already there).