This is a 5 layer folding tetrahedron puzzle. The goal is to go from the unfolded linear configuration to the folded tetrahedron configuration. This is farily difficult so be prepared to struggle with this puzzle for a while before you find the solution!
There is a string that runs through all the pieces which connects them and allows them to spin. The hole for the string is 2.5mm diameter. It is best to use a string that is not elastic.
You will need to print one of each piece except you will need 2 of piece 39 since it is the cap to cover the ends of the string. I have made and STL with all the parts nested together and i have made two STL's each with half of the parts nested together (in case of a smaller print area) and i reccomend you print those rather than each piece separately.
First cut a length of string of about 750mm (this will make sure you have plenty of excess). Then tie a knot at one end of the the string so that the knot cannot pass through the hole in the pieces.
Each piece has two holes and one of the holes is numbered. The string should first enter through the piece numbered 1 then enter the piece labeled 2 etc. The string should always enter the hole with the number on it and should exit out of the unlabeled hole.
Once every piece has been placed on the string tie a knot at the other end of the string so the pieces cannot come off. It is important to pull the string as tightly through the puzzle as possible before tying the knot. Also, try to tie the knot close to the exit hole of the last piece some tweezers can help with this. Once the last knot is tied you can pull any exess that might still be on ths string and use some hot glue to hold the excess in place. This will ensure the pieces are held as close together as possible. Lastly just place the caps over the ends to conceal the knots and the hot glue. Spend some time to get a good knot and to pull all the slack out because it really helps.