How It's Made Season 21 Episode 2 Powder Horns, Handcrafted Molds, Pierogi, Inner Tubes ( Air Date 2013-04-11 ) Genre Documentary category. Overview "Animal horns are cleaned, heated, shaped and polished before being fitted with plugs and pouring spouts for use as traditional powder horns. Craftspeople produce precision moulds for decorative glassware; rounds of dough are folded around savoury fillings to make pierogies; and rubber tubing is extruded, joined, fitted with valves and vulcanized into tire inner tubes.".