I found this drill on the Xavier Men's Basketball Newsletter Site.
I like to use this and other tweaks to the traditional shell drill to practice defending most of the types of cuts and screens that we face.
I like to do that because it also gives the helpside defenders practice on what they will be doing as those actions are taking place.
We defend ball screens, down screens, flare screens, baseling drives, post feeds, and all other actions during our shell drill sequence.
I like to use the traditional no movement shell drill as just a "positon check" and spend most of the rest of the time in the shell working on defending other movements.