The second step in the investment casting process is creating the pattern assembly. In the vast majority of casting runs, more than one part can be cast at a time for efficiency and speed. To accomplish this, two or more (often many) patterns are attached to the sprue, which is a structure that will enable molten metal to be poured into multiple cavities from a single entry point. Craftsmen skillfully assemble the structure using hot wax to optimally place each pattern.