US Patent 7390139 Boss assembly for threaded coupling

A minimal volume boss may be formed as key and keyway assembly defining a shaft along the interface between the two pieces. A threaded fastener may be threaded into the shaft to lock the two pieces together. Because the key can have minimal volume, the cavitation spot opposite the key, typically formed during molding can be eliminated on fine surfaces. By properly keying the pieces, rotation between parts can also be eliminated. This helps automated torque sensing tools read and apply the proper torque in automated assembly.