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The Doornail is a very interesting interlocking puzzle from Brilliant Puzzles, and prior to get this version I already knew the concept: In my collection, I have a simpler version with six rods and about half the size. You may also know it as the Computer Chip, which in my opinion is more fitting.
The concept of the Doornail is similar to a traditional burr puzzle, where notched rods are interlocked and intersect at right angles. In this version, eight rods are interlocked inside a square box with four on each side. The object is to get all rods out of the box and then return them to their original position. It's a fairly challenging task, but if you carefully analyze it, it's actually quite simple to solve. Its dimensions are 8.5 x 8.5cm (3.3").
Brilliant Puzzles rates this as a level 4/5 difficulty, and in my opinion it all depends on how good you are at solving burr puzzles. Just like any other burr puzzle, to take it apart you need to find the "key" rod. In other words, there should be a plain rod without any notches, which would be the first one out. After you get the first one the others won't be a problem. The real challenge, however, is to get all of the pieces back in their original positions.
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Again, if you're used to solving burr puzzles, you'll know what to do. The first thing you should do after getting all the rods out is to arrange them by groups: If you look closely you'll see that there's one rod with four notches, two rods with three notches, two with two notches, two with just one and finally the plain rod. Just like when you were taking them apart one by one, reassembling the puzzle requires a specific sequence that needs to be followed, which is the complete opposite of the first task. You'll start by the four-notched rod and work your way to the final plain rod. The strategy is pretty simple: with every new rod you place, you have to make sure you leave all remaining slots free for the other rods. Once you place a rod there's no need to move it again.
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The Doornail was an enjoyable puzzle and a satisfying challenge. This is a must-have for any burr type puzzle fans and if you fancy a good challenge, it's worth a try. Even if you're a beginner, I'm sure you'll eventually find a way to solve it. Just give it a chance.
Availability: You can get your Doornail from the online puzzle store Brilliant Puzzles for just about $9 USD.