Shingles are designed to be installed using special wide head roofing nails. Each shingle has a designated “nail line”. If shingles are fastened outside the nail line the manufacturer’s warranty is voided and the roof assembly is out of code. This also leaves the roof susceptible to roof blow-off in the event of strong winds. In 1994, when the new code system was introduced, the requirement was 6 nails per shingle. It has since been reduced to 4 nails per shingles. However, most of the good roofing contractors still install 6 and in order to achieve the enhanced wind warranty, 6 nails per shingle must be installed.