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The idea of using a marked staple to cue a folded, stapled billet was contributed to Pabular (Vol. 1 No. 4, Dec. 1974, p. 39) by Bob Ostin. Dick Koornwinder has also done work on the idea, which may not published: He uses a steel staple among bronze ones, or cuts one leg slightly shorter with a nail clipper, or roughs the surface with a knife, which preparation isn't visible, but can be felt.