How do you make corrugated iron for modelling?

The easiest way is to buy sheets of corrugated plastic.

I have used the corrugated inserts inside an After Eight mint box in the past, but if you like to scratch build and require a large amount, I would suggest buying something called a tube squeezer. This is a tool made of rollers designed to help dispense toothpaste from a tube.

By using a thin piece of card covered in aluminium cooking foil you can crimp the foil by passing it through the rollers, leaving you with a length of corrugated foil.

It is advisable to glue the foil to the thin card first with PVA glue.