One of my hobbies is blacksmithing (not ferrier work). Mild steel is an amazingly versatile material. It's very strong and hard at room temperature and it gets soft and easily workable when you heat it up. You use a hammer to move the metal once it is hot. You don't have to hit it very hard, just firmly. Hot metal is a very forgiving medium. If you make a mistake, simply heat the work up and try again. You rarely encounter mistakes you cannot recover from and you have to throw your work away.

A blacksmith uses tongs to manipulate work that would otherwise be too hot to handle. You don't want to drop a piece of hot steel, so you'd like your tongs to be a good fit on your work. Find some tongs that are an approximate fit and stick them in the fire to get good and hot. When they have softened, put the hot tongs around the cold workpiece and tap them into shape with your hammer. Voila! Custom tongs.

When I first saw this trick I was quite amused. It reminded me of Lisp programming — you can work on your problem, or you can customize the language to fit your problem better. And, yes, I'm the kind of nerd that sees a blacksmith trick and thinks “Lisp!”

Another computer-sciency question is one of bootstrapping. Where do tongs come from? How do you make tongs if you don't have them? This isn't too hard. A simple pair of tongs is basically two sticks with a rivet. You can shape half a pair of tongs (a single tong) by holding one end while you work the other. It will take a bit of time for the end in your hand becomes too hot to hold.

A good part of blacksmithing is creating ad hoc tools in pursuit of the end goal. You fairly often recur and create tools that help create tools. Metacircular blacksmithing.

The downside of working hot steel is that it is quite hot. You will get burned, but usually only mildly. Your reflexes take over pretty quick when you touch hot metal. Then you learn early on that if you drop something, you do not attempt to catch it.