Chunky Metal Brain Teaser Puzzles _ Set of 4 SET of 4 take-apart Chunky (strong) Metal brainteasers. Bonus Twisted Nail Take apart puzzle. An additional puzzle is to rejoin the two halves back together. 1 Puzzle Rated: Medium, Difficult, Tough and X-tough by manufacturer. Your experience may differ Twisted Nail Puzzle is Fun. A little tricky. Stumps most puzzlers for at least 5 minutes. These are strong puzzles. However NO force is ever needed. Just clever movements.