Rapson's slide
noun
Rap·son's slide
ˈrapsənz-
: a device that consists of a crosshead capable of moving in fixed guides and having a pivoted block with a hole in it through which passes a lever hinged at a fixed point outside and that is used as a differential gear for a ship's rudder
Word History
Etymology
after John Rapson, British millwright who patented such a device in 1834