[bob jenkins]

Originally Posted by just another ref

Here's the problem with the twist. Defender is stationary, with the dribbler coming straight at him. At the last possible moment, naturally, the dribbler makes a move to try and go around. The defender makes the twist described above. He may or may not move a foot. Trouble is, most fans, and, let's face it, some officials, say "He was moving," and call a block.

Or, s/he may move outside his "cylinder" after the offensive player became airborne. Then, the block is the correct call.