CompTrans is a simple Matchbox Transition used for clips with built-in alphas that act as custom wipes. Usually you'd stick such a clip on a higher track overlapping the outgoing clip, but if you have a few of these in a row, you wind up making staircases on your timeline which I hate doing if I can avoid it. CompTrans lets you do it inline on the same track as a transition.

Grab it from the Logik Matchbook if this sounds useful to you.