I bought one of these one-handed queen catchers last year and had no problems marking my queens with it.
But I’ve since heard from a few people who have had problems with it — one beekeeper even squished a queen with it. I wrote about some of the minor problems I had with it in last year’s post, How To Mark a Queen Bee, but none of them were deal breakers for me.
Until this year when I tried to mark a queen and I couldn’t pin the queen because the foam bed she sits on wasn’t high enough. Maybe the foam shrunk over the past year. I pushed the plunger all the way up and the queen kept running around. I suspect this is how someone squished their queen. They must have kept on pushing until the queen got flattened.
In any case, I super-glued a hard but not too hard piece of foam on top of the plunger to reduce the space where the queen can wriggle around. After that, I had no issues with the queen catcher.