The Penrose triangle, an impossible-looking shape, is made by welding metal pipes together. First, the metal pipes are cut ...

It helps make things clearer when you start cutting your metal. And you're ready to start cutting. Check out 'Explain This… Cutting a shape from metal' for what to do next. This short film ...

Then you'll need to use a step drill for accuracy and to stop the metal snagging or tearing. Edges are shaped and flattened by cross filing, smoothed by draw filing and softened using an emery cloth.