Catches on the fins. AFAIK, it fits everything with that style alternator.
I've seen crowbars crack the cases on the alternators, so I always used to just pull on them while tightening the clamp bolt. It's a little hard for me to do that these days, so the tool comes in real handy.
That's how I've been doing it - for my 383 I wedge it between the block and the alternator and push the alternator out/up as much as I can while I tighten up the bolt.
