This project was inspired by Jonathan Rochelle, who also has an excellent design for a snap-together bracelet for kids.This is a conceptual derivative of Jonathan's design. I did not use any of his files, rather I designed something similar myself after looking at his photographs and description.There are two styles of empty block units that link together like Jonathan's, but they have no top part. Then there is also a press-fit top that can be customised and pressed onto each block.Each block is linked to the chain with an easy place-and-twist action, so long as the blocks are held at 90 degrees during the linking (see photo), but then the links won't come apart by pulling or shaking them.The earlier version was not very stiff, and tended to bend too much when joined. This version is stiffer - a bit harder to join but also much harder to accidentally come apart.There is also a special pair of click-fit joiners for easily closing and opening the bracelet with one hand.The press-fit tops are designed with a tight tolerance, so they will need to be pushed in hard, and they will not pop out without a lot of force.I have included STL files for the digits 0-9, and capitals A-Z, and a star design. This should give most kids a fairly good start with the bracelet.The idea is that a bunch of the generic blocks can be pre-printed, maybe in many different colours, and then the kids can have customised press-fit tops to add them in whatever order they like onto a linked bracelet for themselves.Each empty block takes about 7 mins to print on my Printrbot, and the press-fit tops need less than 5 mins each. There is no support material option required with these prints.UPDATE: 12 May 2015 - fixed an error in with Block Unit 2, and reuploaded Sketchup file and STL file.