Good defensive rebounding drills are hard to find.  One of the hardest box-outs is trying to get and maintain a body on a moving opponent when a defender is stationary.  This drill attempts to address the difficult skill of boxing out.

This drill only uses half of the court, so you can have 2 sets of players performing at the same time.  Position 4 players at each of the keys (#1, #2, #3 and #4), and one additional player (#X1) positioned under the basket with the basketball.  Position a Coach near #X1 at the basket.