The pants racks are designed to fit into our towers, not the double hanging.
The design tool will not allow you to put it there.
If you'd like to install it in the bottom of the double hanging you can, but there are a few important things to keep in mind:
1. You'll need to drill your own holes.
2. The slides will stick out 3/4 inch from the unit because of the cleat at the back of the unit
3. Make sure the double hanging unit is 19.5", 25.5" or 31.5"
4. You'll need to add it to your cart separately because the design tool won't allow it