These brackets are designed to securely hold flower boxes to the top of a deck or porch railing. Fasten the brackets down to the rail at your preferred distance apart and boxes are captured within the U-shaped holder. In two widths to fit standard 4 and 6-inch railings. Use with Embossed Flower Box (C-04) or Small Galvanized (C-08) or Small Copper Plated (C-08C) Flower Box.