Keystone Hardscapes 87670 6" Anchor™ Highland Stone® 3-Piece Retaining Wall System Sand Brown/Charcoal. The Anchor™ Highland Stone® 6-Inch Retaining Wall System is designed with the texture and look of natural stone. This unique three piece system offers a hand hewn facing that accommodates a stone like appearance. With the patented rear lip, setback and alignment are facilitated resulting in faster, more reliable construction.