If you look at the picture I posted of my completed print, one piece was printed in two halves. This is so you can take one half off and look at how the joint is held together. The file final joint-1 goes with table leg joint, I just did not name them the same thing as there were multiple print attempts before I got it satisfactory. Also, for the table leg joint, print two of each object shown to get the complete joint.
These are 4 joints commonly used in woodowrking. They would be great for younger kids who are just starting woodshop to look at and play with to see how it all fits together. One of these joints costs only a couple dollars to make for a model you can hold and take apart. Online there are posters of joints for about $10-$20 from what I saw (link to a poster below). With posters you can only look. I know I prefer something you can hold and examine, especially for woodowkring which is a very hands-on task.