October 17, 2011

Interlock Four

Interlock Four is a nice little four-piece puzzle designed by Stewart Coffin. This version was crafted by the folks at Creative Crafthouse, and they were kind enough to send me a copy to review. Thanks!

The four pieces assemble into a 3x3x3 cube and are serially interlocking, meaning that the pieces must be added in the correct order. This makes it somewhat more difficult, since you may need to backtrack a bit if you don't get the right order to start with.

It is a good size which gives it a nice heft, about 3 inches square and weighing about 9 ounces. The finish is quite good: it has been sanded smooth and given a nice bevel on each cube. It appears that the cubes were beveled before they were glued up, which looks great and adds to the difficulty since it is tricky to see where the glue joints are. The fit is also quite good!

As a puzzle, I didn't find it particularly challenging, but I've done a number of assemblies like this before. I think it took me about a minute to get back together after taking it apart with my eyes shut and scrambling the pieces. However, it is a good one to give to folks to get them started thinking about this type of puzzle before you get on to more complex assemblies with more pieces, or which require multiple moves to extract the first piece.

I think what made this one easy for me is that if you take a logical approach, you can quickly determine what goes where without too much trial and error. As such, it is a good puzzle for demonstrating those techniques. I showed this one to my wife to see how she would do with it, and she had a good time with it. I gave her a few tips on how I would suggest approaching it, and she solved it in about 5 minutes.

I'm sure a lot of you do this, but in case it helps somebody I'll briefly describe my approach to this type of puzzle. I start off by trying to find the biggest piece and use that as my starting point and keep it in a fixed position. Then I try to find the piece that has the fewest possible orientations relative to the starting piece and narrow down my options for the other pieces from there. Some puzzles you'll have a lot of options, or there won't be an obvious starting point, and those will take me a lot longer.

One great thing that the folks at Creative Crafthouse have done is to put up a video for each of their puzzles where they describe it. You have to be a bit careful, since there are spoilers sometimes, but usually you can see it coming or you are warned beforehand. Check out the video for this puzzle here, but be aware that he disassembles it from 0:09 to 0:26, so shut your eyes during that part if you don't want to see that. You can look again after he says "there's the last two".

Overall, I liked Interlock Four. It is reasonably priced at $15 for a sturdy and well made puzzle. Definitely worth checking out if you're into this type of puzzle or want to try your hand at an easier cube-assembly puzzle.


  1. It's a less general technique, but it can also be useful to keep track of the corners in the final cube. In this case, the largest piece must fill 3 corners. The two smallest pieces can fill only 1 corner. Thus, the remaining piece must also fill 3 corners.

    Incidentally, I just noticed that all the pieces can be made by gluing two L's together (either L triomino or L tetromino). I wonder if this is how Coffin designed it?

  2. This is the first interlocking cube puzzle I bought, and I still like it. Did you notice that one of the pieces is shaped like the digit 4? This is even pronounced when it moves in/out of the assembly.

  3. Ah, I didn't notice that! Perhaps another reason for it being named Interlock Four


Please don't post spoilers! Thanks for commenting!

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