Remember when Disco. spinner Casey Luskin rolled out this silly attempt at refuting critics of irreducible complexity?:

Car engines use various kinds of bolts, and a bolt could be seen as a small “sub-part” or “sub-system” of a car engine. Under [Ken] Miller’s logic, if a vital bolt in my car’s engine might also to perform some other function—perhaps as a lugnut–then it follows that my car’s whole engine system is not irreducibly complex. Such an argument is obviously fallacious.

He wrote that in April of 2006. Little did I know at the time that the Department of Homeland Security had issued a document in March of that year which could have clarified matters. In What Every Member of the Trade Community Should Know About: Distinguishing Bolts from Screws, DHS advises importers and customs agents about the proper way to categorize threaded metal for purposes of tariffs. As a matter of definition, DHS explains:

<blockquote>A bolt is an externally threaded fastener designed for insertion through the holes in assembled parts, and is normally intended to be tightened or released by torquing a nut.</blockquote>

If a bolt were also a lugnut, it would be very confusing.