John Hall wrote: > > Beno, > Why the tyres? > What's wrong with just the gravel? > Rubber compresses, and decomposes with time. > Can't see any advantage. > John. Well, I thought the tires would give form: like big flat boulders upon which to build.No slippage. Actually, I read in the archives (after posting) a couple years back that apparently this is done...even used in walls! beno