Heritage Brass Black Iron Rustic Range. Our Black Rustic Range is produced with molten iron flowing into cav1ties in a sand mould and made malleable by a process known as annealing.  The surface of this product will reveal slight indentations created as the metal cools while the shape is being formed to bestow an aged look. After casting the iron is treated with a process called Phosphating which slows the rusting process.  It is then coated with a powder coated black finish. Any iron product is prone to rusting so all external parts should be regularly wiped over with a lightly oiled cloth. Also periodically any moving parts and springs should also be oiled. This is a decorative square knob with 4 small surface squares on top