When fitting and positioning parts during construction, reference is frequently made to other construction objects, e.g. if you insert a hole relative to the centre of a hole in another part. This reference between two parts is called external reference.
Example:
When inserting the hole in part 2, the centre of the countersink of part 1 is defined as an external reference. If this reference part changes its position, the hole will also change position so that the defined distance remains the same.
External reference between two parts
If you want to prevent such reference, choose the Processing external reference: Do not use function. 
Related Topics
Version 1702 - HiCAD Feature Technology | Date: 9/2012 | © Copyright 2012, ISD Software und Systeme GmbH