Working with Purchased and Multipurpose Parts - Autodesk Inventor 2010: No Experience Required - page 291

FIGURE 6.37 Aligning the caster to the bottom of the assembly
FIGURE 6.38 The completed location of the caster
16. Place another instance of the caster, and constrain it to the assembly
on the other side of the assembly per Figure 6.39, using the same
distances.
17. Save your work.