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Puzzle Solving/nail balancing


a teacher wrote at 2006-07-08 22:56:53
My hint: Use gravity as your friend. Rearrange the nails in ways that they lock into each other without falling off, then balance the midpoint on the nail. good luck.

StevieP wrote at 2006-08-13 07:07:48
The solution is actually very easy, although not obvious.  First, lay a single nail on the table.  Across each end of that nail, lay two nails next to each other but in opposing directions such that their heads are about 1/8" or so from the shank of the first nail.  When you have this step complete, your collection of nails should look almost like the letter H.  Place the last remaining nail on top of the all of the others such that it is parallel with the first nail, and rests in the cradle formed by the other four.  Gently pick up the whole assembly by the ends of the bottom-most nail, and place it on top of the nail driven in the wood.  The four crosswise nails will angle down, with their heads firmly locked in place by the topmost nail.  They will also keep the center of gravity low enough to keep the finished product remarkably stable when balanced on the nail in the wood.

Note that the block of wood is just for convenience, and you don't need it to make this trick work.  Consequently, you can do this trick anywhere that you have seven sufficiently long nails.

JPR wrote at 2006-12-13 15:16:36
Nail #7 is the nail in the wood block.

Step One:  Lay nail #1 flat on a level surface.

Step Two:  Place nails #2 & #3 in the same direction as each other on top of #1, with the shaft of #1 just under the heads of #2 & #3, perpendicualar to #1, equidistant from the center of gravity of #1, a minimum of 1" apart .

Step Three:  Place nails #4 & #5 on #1 meeting the same criteria for #2 & #3 in Step Two except for the last criterion (the 1" spacing), in the opposite direction of #2 & #3, adjacent to #2 & #3.

Step Four:  Place nail #6 on top of #2, #3, #4, & #5, in the opposite direction of #1, with #6's center of gravity directly above #1's center of gravity.

Step Five:  Using index fingers, slowly & levelly lift #1 by its ends allowing the nail heads of #2, #3, #4, $ #5 to interlock around #6.  Repeat Steps One through Four until all nails are interlocked and balanced.  Place center of gravity of #1 directly atop #7.

Puzzle solved.

Okra wrote at 2009-03-19 02:07:27
Hint: This puzzle is also known as "The Tin Roof"

Hint: It's much easier to get the six nails together first, and then balance them on the one.

Hint: Maybe there's a way to make them hold each other in place?

Still can't get it?


Lay the First nail (of six) on the table (surface) in front of you.

Lay the Second nail perpandicular (at a right angle) to the First, so that the heads touch; they should make an "L", not a "T".

The Third nail goes next to it, similarly, but with the body of the nail on the other side. It should look like a "T" now, with one arm slightly lower that the other.

The Fourth and Fifth nails should go across the first in the same manner, but at the other end of the First nail, the whole structure resembling the letter "H".

The Sixth nail lays on top of the heads of the Second, Third, Fourth, and Fifth, in exactly the same manner as the First nail, but with the head on the other end.

You whole assembly should still look like a capital letter "H", with the top arms being nails Three and Five, and the bottom arms being nails Two and Four. The middle should be nails One and Six, stacked in opposite directions.

Lift this "Tin Roof" by the ends of the First nail, and balance it on the head of the nail driven into the block.

MJS wrote at 2015-02-02 21:29:16
I know the answer to this, but in the 20 years that I've used it as a team-building event, I've never seen it solved by a team. It takes more than 2 hands to arrange the nails in the correct structure. That is a hint that I usually priced to help the teams understand that it's not a one-person puzzle. So here's the answer process.

1. Place one nail tip down into the block of wood

2. Hold a second nail horizontally in the air

3. Take 2 nails in your other hand and cross them at a 45 degree angle about a half inch from the heads.

4. Have the other person do the same with 2 other nails

5. Insert your single, horizontal nail below where your 2 nails cross, so that the 2 nails are near the head of the horizontal nail.

6. Have your partner place his 2 nails in a similar fashion at the other end of the horizontal nail

7. Place the final nail horizontally, above and parrallel to the horizontal nail so that it is pinched by the heads of the crossed nails

8. Find the balance point of the horizontal nail by moving your finger under it until it balances

9. Place the balance point of the horizontal nail on the top of the nail in the wood so that the structure balances.

10. You're a genius!  

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Bernard Hawkes


Please read my Policy Statement. Puzzles and brainteasers. Ask and I will help! That said, I`m best at pure logic puzzles. E.g. You have twelve apparently identical coins of which one is counterfeit, being either slightly heavy or light. Determine the counterfeit coin, and whether it is heavy or light, in no more than three weighings using a balance scale. Rebuses and riddles I`m less good at, but will generally get the answer given time. Requests for oddball facts (e.g. What was the second most common girl`s name in 1900? [genuine example - answer: Ruth]) I regard as outside my remit. However, you are welcome to ask, but I may not be able to help you.


Member of Mensa. Solution to "gry" riddle.

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