These were an amazing tool to work on my motorcycles and Mini Bikes when I was young.... All used philips head screws that no matter what you did you stripped out the heads unless you had one of these....
I believe alot of the Jap bikes used these to tighten the philips screws during assembly which is why they were so hard to remove.....
I started using them in the AF on stuck panel screws.
Very simple to use if you understand how they work. I've seen [lots] and I mean a [ton] of people who have no clue.