bolthead

bolthead

(ˈbəʊltˌhɛd)
n
1. the head of a bolt
2. a spherical flask with a cylindrical neck, used in chemistry
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in classic literature ?
If I'd a called it a bolthead it would a done just as well.
It has a rotating bolthead with three locking lugs, and the locking lugs are 0.87 inch in diameter.
A detail numerous female Sydney Boat Show visitors liked, according to Chris Pomfret of Sydney Yachts, was the easy to clean, fully moulded headliner that hides boltheads etc.