P. C. Herwig Co. was a Brooklyn craft supplier and publisher run by Philip C. Herwig. The company was in business by 1926, when it copyrighted one of its square-knotting books. A 1938 ad called the company “Square Knot Headquarters” and offered cord, instruction booklets, and beginner kits for making belts, purses, and even dog leashes. Square-knotting is a macramé technique.

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