I got a twisted nail puzzle yesterday from a science toy shop. This twisted nail puzzle has two twisted nails , if you interlock them its very difficult to seperate them. You need to know the trick to seprate nails. My five year old Kid Aatish was able to solve that puzzle in a minute. I just showed him once the process of solving it.
Here is the video of Aatish Solving twisted nail puzzle.
It seems very simple by looking at video. But if you actually try to solve this puzzle , you will appriciate Aatish :).