Carderock® Garden Wall Stone - irregular in shape and somewhat flat, this grade of stone is ideal for dry of semi-dry stack retaining walls up to 24" in height, such as those defining a raised garden bed. With one reasonably good face, 8" to 12" deep, 3" to 6" in height, up to 18" in length, coverage of 18 to 20 square feet per ton can be expected.