Robin had the single face corrugated cardboard donated. You can find
this product real cheap on line (sold by the roll) - or look locally
where they sell packaging materials. (Sax does not carry it - I
checked. They do sell a finer corrugated paper that would work - would
make much finer lines)
This lesson is good for upper elementary on up. Older students can
make larger, more complex plates. Robin did it with 4th and 5th grade.