Timber is used to build the framework for the moulds, supporting it while it is being constructed.
Metal is a material that is used to make running moulds, usually zinc and occasionally steel. Steel is better because it does not bend when there is heavy weight but it is is harder than zinc to file and cut. The metal is cut into a plate and attached to the running mould to create the template.
Nails are another material that are used to create running moulds. You must make sure you use the right size nail for the timber you are using as you do not want it to go right the way through.