This is a simple example of using some generic prints to make a quick useful tool.  In this case hand winding a custom transformer.  

This print is too simple to really post by itself but here to illustrate how quickly can adapt some simple parts to make useful tools.

Trying to hand wind this particular transformer was hard by hand as all the pins bite your fingers on every revolution and hard to maintain uniform wrapping.  

This builds on these prints:-

https://www.printables.com/model/161342-generic-construction-tools