For my birthday this year I was lucky enough to receive an Electric Tooling Iron. This is a tool that book binders use for marking their books with metallic foils or for marking directly onto leather. It might be words or just decoration. Below is an example of how you would use it.
First you need to know what you are using it for. In this case I have traced the title of one of my favourite books, which has a beautiful title font. I would do this if I was repairing the book and going to replace the cover.
First the metallic foil needs to be stuck to the new cover with masking tape. It must be perfectly flat.
The tracing is then placed over the foil. Using the iron, once it is hot enough, you trace the design onto your book. This takes a little practice as you can't hold it as close to the tip as you would a normal pen. It doesn't matter too much if you need to go back over it as long as your design doesn't move half way through.
The finished design. If I had another coloured foil I could go over it again as long as it was lined up right.
This is a great tool and I look forward to having some more practice with it.