In the workshop you oftentimes need to make sure things are square, meaning that a certain corner is right angled. Sometimes the things you need to check are small, which makes using a big square somewhat of a hassle. If you have access to the right machines, and you're cheap like me (but have a bit of spare time) why not make your own miniature square?
This is not a beginner's project, and does require some knowhow and experience around a machine shop. Avoid costly mistakes, and especially those involving bodily harm.
Steel, I used scrap I found around, though the harder the steel the better finish you're going to get and the longer the tool will last.
Brass, though used stylistically, could be steel as well
Milling machine, with endmills of various sizes
Files, and possibly fine grit sand paper
Taps and dies
Solder iron or torch
Hope you enjoy the video!