For countertop installation mounted over a knee/pony wall, then into each stud on the knee/pony wall, to secure the weight of the countertop. If no knee/pony wall, then a 2x6 must be mounted inside the cabinet and the L Bracket attached spacing every 16-20 inches. **Not for use in any other application than that listed. When determining the size: bracket is sized in length tip to tip horizontally; for example, a 9-inch bracket is 9 inches tip to tip horizontally. Do NOT include the 6-inch vertical piece when determining the size to order. Tip on determining length: stay away from outer edge of your countertop 2-4 inches and do not forget to add in the thickness of the knee wall, pony wall, or the 2x6 inside the cabinet. For example, only: a 12-inch countertop overhang, plus 4-inch knee wall, equals 16 inches, minus 3-inch outer edge, would mean you would order a 13-inch L-Bracket. Made of 1/2" thick by 2.5" wide solid American steel on the horizontal piece and the vertical piece [tang] is made of 1/4" X 2.5" X 6" long wide solid American steel. This is for one (1) bracket only. Still not sure, call us 888-584-1112 we can help!