Love the idea, Yvonne.I used rectangular stepping stones at the bottom of my fences ( called masonry caps).
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I realize this doesn't help with your solution and I don't know if this the standard but as soon as we got Herm, he went to work digging a burrow (in the middle of his area under a large creosote bush) and he never attempted to dig anywhere else. It's been 12 years now. I guess he is happy with his creation.