There are few things more pleasing than watching people who believe they know everything humbled by such a simple feat of puzzle engineering. Come and have a go if you think you’re hard enough! The perfect gift for someone who wants to test their nerve and dexterity -These puzzles are very challenging and offer hours of fun individually or with friends and family. Although these puzzles may cause frustration and mental exhaustion the sense of achievement in solving a puzzle cannot be underestimated! Nail Jail Puzzle Slightly more difficult than the Nail Biter. The simplicity of this puzzle is well hidden, so it takes longer for even the most seasoned puzzler to get to grips with the mechanics of it.