Bury stones to make a mow strip If you're building a fence, a retaining wall or a planter, set a course of protruding stones in the soil beneath it. That way, your mower can cut all the grass—no trimming by hand needed. The stones should protrude about 4 in. from the wall and stand at least an inch above the soil so grass doesn't creep over them. You will still have to pull out grass from between the stones occasionally.