Courtesy rigging is used when you need the rapide positioned over the lip of the drop for a clean pull, but when you want to give all but the last person an easier rappel by temporarily locating the rapide farther from the edge.
There are lots of different knots and ways that you can tie your ropes, but here is the general workflow.
If you want to save some rope and not rig two independent sets of fixed webbing, you can rig the shorter rigging with a frost knot or with a water knot and overhand on a bight. Then you can thread the longer webbing with into the frost knot or overhand on a bight in a follow-through fashion.