Regular old sand like you would use to mix with concrete. $2.50 a bag. Outdoors, in will just mix with the soil. Don't terry too long in one spot or you will warp the metal. I sift my sand first, it has big pieces and staples, etc. in it. That takes a little while but I have a sifting station set up. Not play sand, not washed sand, not silica sand, just sand. BUT it MUST be sifted.
Last edited by bartamos; 08/04/2010 1:42 AM.
