A mechanical engineer or designer focused on manufacturing and assembly processes, possibly working with machinery or equipment requiring fasteners, or a hardware supplier or sales professional catering to industries that use bolts and nuts, such as construction, automotive, or aerospace.
My day involved a surprisingly large number of Allen wrenches, and I swear, one of them winked at me.  You know, it really makes you appreciate the little things in life, like perfectly-torqued fasteners and the satisfying click of a properly tightened bolt.