Planishing is done using what is called a ball stake or planishing stake. It has a rounded part at the top used to shape the metal pieces. Striking the metal and making it conform to the curve of the ball on the ball stake is the act of planishing. The ball always needs to be smaller than the piece being planished. Ideally the size of the ball should be representative of the amount of curve the planisher wants in the steel to make the process easier.
Planishing hammers have a large and flat surface as they are designed to work with broad areas of metal. Its use requires the presence of the planishing stake to shape the metal pieces against. The stake maintains its position by the planisher using a vice to grip it in place. Another way to stabilize it is to place it in the mounting hole of an anvil. The planishing hammer can produce a variety of shapes, but the stake has to be shaped to create the curves the planisher wants to achieve when he shapes the metal against it.
The word planish came into English from the Latin word planus. This word means flat so it was a fitting name for the tool. The flatness of the tool is significant because unlike ordinary hammers you would use to strike small areas such as the heads of nails, planishing hammers are made to work with wide, flat pieces. The flatness exists, at least to begin with, for both the hammer and the piece being planished.
The idea of planishing metals is very old. The first planishers were medieval craftsmen who used the method to shape armor needed in those times. As they were then, manual handheld planishing hammers are still in use but technology has provided some easier methods. These include foot-powered devices as well as pneumatic and hydraulic devices that make the work much easier. Manual hammers have not lost their importance despite these advances since they are necessary for shaping small pieces of metal and adding final touches to shapes.