Groovy Blocks

This puzzle starts with a collection of blocks. The blocks have some grooves cut into opposing ends.

Players will probably quickly realize that although there are several different patterns, some of the patterns line up. Players will probably try to line up the blocks to make the grooves continuous, but this will not work for more than a pair of blocks.

The trick to this puzzle is that the blocks need to be stacked vertically rather than arranged horizontally. When stacked, the groove patterns can be matched up. More importantly, the holes formed by the grooves form a pattern of numbers.

Looking at the side of the blocks, the code is 8347.

This code was chosen because it results in a different groove pattern between each pair of blocks, and none of the patterns are palindromes. This means that there is only one way to arrange the blocks where all the patterns match. Also, viewing the numbers upside down or inverted does not show all proper numbers, so there is only one way to interpret the numbers from the side.

Solving the groovy blocks puzzle can be tricky and might take the players some time. I recommend providing the groovy blocks well before their code is used so that the players have other puzzles to work on while they figure this out.

The groovy blocks in the examples above were created with a 3D printer. If you have a 3D printer, you can use this STL file.

If you don’t have a 3D printer, there are other ways to make matching grooves. One way is to use a table saw if you have one. Cut up a 2x4 into equal blocks of an appropriate length. Then set the blade low so that the wood can be passed over the blade to cut a groove but not all the way through the wood. Set the fence to guide a block to cut the groove the appropriate distance from the end of a block. Keep the fence in place to cut each groove that matches opposing blocks.

You can use this pattern to guide the placement of the fence and where to cut the blocks.

If you don’t have a way to make precise grooves in blocks, an alternate approach would be to draw lines instead of grooves. Use a square tool and a pen to draw lines perpendicular to the edge of the block. Hold two blocks together to make sure that the lines match up. Make sure the lines spill over the edges so that the locations, and hence numbers, can be seen when the blocks are stacked correctly.