So you have an assembly and have been given the task of inserting multiple copies of the same part into it. The question then becomes what is the fastest way to create all of these instances and have them properly mated into position. As with most tasks in SOLIDWORKS there is always more than one way to get the job done.
The first is if you are going to use the part file on a continuous basis then you can utilize Mate References. Mate References are found in the Reference Geometry Sub Menu on the Features Toolbar. In the Mate Reference property manager you specify different geometry for the First, Second, and Tertiary Mate. For each mate you can specify a specific Mate type based upon the selection or go with the default. You can also specify a Mate Alignment for each mate as well. Generally you will then want to add you file with it Mate Reference to the SOLIDWORKS Design Library so that it can be used again just by dragging and dropping from the Design Library.
The second option is the one I personally use the most and that is Copy with Mates command which can be accessed through the Insert Components sub menu from the Assembly Toolbar. This is very easy to use, it gives you the ability to Repeat if the Mate is going to be same, Flip Alignment and even change distance or angle depending on the mate type you select. This a great option if you have more than one of an item to insert into your assembly.
CATI Support Team Leader