"I dumped the bag of rocks out onto the surface and started moving them around until they looked good. The instructions said that it was best to have them 12-18" apart so I tried to put one at least every 12" with a few extras in between since it's for a 4 year old. They came with 3/8" T-nuts and socket head cap screws so I marked the position of all the holes, drilled them out, installed the T-nuts, and then screwed the rocks on."