National Sheet Metal Roofing Co., Practical hints to builders and those contemplating building (1890)
“ Remember, no cleats or springs are necessary in using our shingles. The lock is simple and perfect, with corrugations across the top, and bracing corrugations across the exposed end of the shingles, which stiffen and hold the shingles firmly to the underlying courses. They are easily applied, and any one who can lay a wood shingle can lay these. We furnish them in four sizes, made from charcoal roofing tin, painted both sides and unpainted, galvanized tin plate, which is superior to galvanized iron, cold rolled copper, and steel plates. ”
