Several of us spent several hours over the Christmas/New Year period trying to solve a puzzle by moving two balls from opposite sides to the same side of the stick. We did not succeed. Then we saw that this puzzle had been rated on a four or five difficulty scale by its manufacturer - as the easiest of all. This did not make us feel any better.
One morning, E5N1 picked it up for the first time and about 30 seconds later he had achieved what had eluded the rest of us - he wasn't sure how, but he was quite happy about it:
I have since worked out how to solve it. Of course, now I know how, I can agree with the difficulty rating it was given!