Reuse Pattern allows the assembly to reuse a pattern that was created in a part. This allows parts new instances of a part to be located at every instance of a pattern. An example of this would be placing bolts in every instance of a hole pattern.
To initiate this, constrain the bolt to the original hole of the pattern. One method to find the original hole is to right click on one of the holes and select Center Graph.
The Pattern feature will be highlighted in the Specification Tree. You can select the Pattern feature, and the instances of the hole will be highlighted. The hole that is not highlighted is the original hole of the pattern. That original hole is the where the bolt should be constrained.
Once the pattern in constrained, then click Reuse Pattern .
The Instantiation on a pattern window will appear. Select the constrained bolt, and then the hole pattern.
Bolt instances are created at every location of the hole pattern. By default, the bolts are constrained to the pattern through a Reused Rectangular Pattern assembly feature. That feature is located in the specification tree and is saved with the assembly. This allows the bolts to always be in the same location as the pattern, even if the pattern were to change later.