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Like Brain Teasers? This DIY Puzzle “Nails” It


I love brain teasers and wood-based puzzles and this is a good one that you can easily make yourself. Basically, all you need is a chunk of pine, a nail, and some boiling water (oh, and a saw and a drill).


It’s called the “Tooth and Nail” puzzle, and it appears to be an optical illusion. It is not.

SPOILER ALERT: How this works is fascinating. After three sections are cut from the wood, one of the remaining “teeth” on the end of the puzzle is saturated in boiling water. This allows the soft pine wood to be significantly compressed enough so that a hole can be drilled through the two center teeth to accept a nail. As the wood on the compressed tooth dries, it returns to its original shape and the illusion is complete.

13 thoughts on “Like Brain Teasers? This DIY Puzzle “Nails” It

    1. You could carve a cannibal king and put a bone through his nose –

      Probably not the sort of thing you had in mind, though.

      1. A puzzle should give you all the required informations, and ask you to find the answer. This one require foreknowledge of the properties of pine woods. So it’s actually more a trick than a puzzle.

  1. It is dried compressed, nail inserted and then expanded again in the boiling water. The puzzle is to figure out how it was done. It is not an illusion; the nail actually goes through the center teeth.

    1. I have used this method to curve archways for doors, windows etc out of standard pine 2x4s

  2. It is good trick but a bad puzzle since it can’t be solved with bare hands and you are given impression that you have to solve it like that. Otherwise it can be solved with axe or saw as well.

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Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and “lazy man’s memoir,” called Borg Like Me.

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