It is shaping of hot metal completely within the walls or cavities of two dies that come together to enclose the workpiece on all sides. the impression for the forging can be entirely in either die or divided between the top & bottom dies. The forging stock, which is generally a round square bar, is cut to length to provide the volume of metal needed to fill the die cavities, plus an allowance for flash & sometimes for a projection for holding the forging.

Shapes: (Closed Die)
Complex shapes that require a minimum number of operations for completion can be produced by closed die forging. In addition, the process can be used in combination with other process to produce parts having greater complexity or closed tolerances than are possible by forging alone.