Ah stencils.....they take me back. A strange paper backed jobby with a flimsy skin that the typewriter keys had to punch holes in before applying the whole thing to a duplicating machine. It wrapped around the drum and you turned a handle round and round until you had printed off enough copies of the page. Any typing errors were corrected by applying a pink nail varnish-like fluid to the error, waiting for it to dry before carefully positioning the thing back in the typewriter and then punching in the correct letters. I’m talking circa 19th century obviously!