Ken Larsen's Backgammon - ANCHORX tactic
Anchor prevention – Stop opponent from anchoring. If opponent already has an anchor, don't allow him to establish a second anchor. If he has a second anchor, don't allow him to establish a third anchor. ANCHORX mainly involves hitting blots that could be turned into anchors or passing on hitting a blot that the opponent is trying to recycle.
Preventing an opponent from anchoring is often more important than making an anchor of your own.