Wall clips should be spaced no more than 12 inches apart. The first clips should be installed 2 inches in from each end of the shelf. The rest are evenly spaced between the first two clips. Use a 1/4" drill bit to drill holes, insert wall clips into the holes, and push the pins into place (or use screws if required for your wall material). The total number of wall clips per shelf should be at least equal to the length of each shelf (in feet) plus 1.