If a guard drives down the lane and the other teams post defender steps up to help the dump off to the post player is going to be open. You might look at like players like Tyson Chandler and think that finishing a dump off pass is relatively easy, but there is a lot of things that go into being able to finish around the basket.
A big key to being able to finish is having the big man have his/her momentum moving towards the basket as they catch the dump off pass. The reason why this is important is because the other teams post defender is going to try and turn to recover and block the shot, and if they gather slowly the chance of getting the shot blocked is a lot higher. However, sometimes whether you come into the finish the right way or not the post defender recovers quickly and still is in a position to potentially block the shot, and that is what this drill is going to work on. Using basketball drills like this will really help with the big mans footwork, hands, and finishing around the basket.