To Copy References by Using a Fence

Place a fence around the area containing the references to be copied.
From the Model tab of the Project Explorer dialog, select a reference.
In the Reference toolbox, click the Copy References icon.
Turn on Use Fence and choose the fence mode.
(Optional) To make multiple copies, turn on Copies and in the adjacent field, type in the number of copies.
Enter a data point to begin the copy.
Drag the reference to the desired location, and enter a data point to place the copied model.