Extrusion is used to form parts of uniform cross section in long strips that are later cut to final dimension. It is usually applied to nonferrous alloys to create low-load parts.
Aluminum base for mounting telescopic sight,
formed by extrusion
Leupold & Stevens
A bar of material is pressed through a die that is shaped in the negative of the final part. The result is a long part with the desired cross section. Cutting pieces to length makes the parts ready for final forming and finishing. Extrusion is commonly used to make aluminum bases for mounting telescopic sights.