External Shrinkwrap Features
Shrinkwrap features reference surfaces and datums within the assembly context, whereas external Shrinkwrap features reference geometry from an external model (part, skeleton, or assembly) specified during creation. Shrinkwrap features can be redefined as external Shrinkwraps at any time, however, the process is irreversible.
You can create an external Shrinkwrap feature in one of the following model types:
An envelope
A part
An empty component