I think it works better than the Park tool with the rounded corner. A flat surface punch, placed carefully at the angle of the spline has much less opportunity to damage the ring.

I would be concerned about this too, Jim. Just not the right tool for the job. However, a clever mechanic who has a bench grinder could shape the business end of a round drift punch to fit up to the notch properly. Still, I'd use the right tool.

I used a piece of 1/2" copper water pipe and a plastic-faced hammer before I got the VAR pliers. All of the damage was done to the tubing and I would cut it off when it got too bad. I had lots of pieces of copper tubing on hand after re-plumbing my entire house. It also works well for driving out headsets.

This thread is sort of making me roll my eyes as people discuss options with no acknowledgement of the BBT-7... I was thinking "do I need to post a giant photo?" I know this says it is a shimano/DA tool, but the lock rings on high end BB's all fit this glorious tool! Then I went to the park site.. .couldn't find it! Maybe they discontinued it!? Get it while you still can and you will wonder why you don't have it already... I have never used this tool on DA or XTR, I bought it for Campy/sugino and other quality bottom brackets and it works perfect. I HAVE the hozan pliers, they are nice. This is better and A LOT cheaper.

Park BBT 7 Bottom Bracket Tool Dura ACE XTR | eBay

All my life I have used the Sugino hook spanner. At least since the mid-1970's.

I often apply the hook spanner while simultaneously applying a cup pin tool, for two-armed (more balanced) torque application!

Upon reassembly, for that final adjustment, I again use both tools. Fist homing in on the exact lockring position on the cup that will allow both the cup and lockring to be turned together into a perfect state of adjustment and tightness.
An additional advantage of this final tightening is that since the cup is turning under high load, the threads get settled much better in the bb shell so the cup stays tight. Otherwise, dirt and rust may conspire to allow this threaded interface to settle while riding, which of course causes a loss of lockring tension.
The threaded interface between cup and lockring is under much higher stress, just those few threads, so needs no help settling.

If a Campag BB , then Tulio's 712 tool engages 5 notches of their lockrings.

One nice thing about the pliers (VAR, Hozan, or DIY) is that they more easily fit lockrings with different diameters, such as those found on track hubs and some headsets.

One shop I worked at had one type of pliers-type that I didn't like-it was hard to keep it from sliding off. Two other shops used another type that worked extremely well. If I had to guess, I think the Hozan tool was the good one. Any other experiences?

Great idea, thanks!