Use a scrap spacer for dead-on drawer guide installation
When mounting drawer slides in the cases, you have to be dead-on accurate and able to repeat this accuracy for all the slides. To do this, lay the cabinet on the side. Then cut a scrap spacer the correct length for mounting the uppermost slides. With the spacer against the case bottom and the slide against the spacer and set back 7⁄8 " from the front edge of the side, drill pilot holes and drive the screws, as shown. After mounting all the slides at this height, cut the spacer to length for the next highest group of slides, and repeat.