My 3xG GF William Todd is in the 1841 census at Spring Garden Lane, Sunderland, age 60, as a waterman. The parish record of his son Lindsay Todd's baptism gives William's occupation as keelman.
The baptism record and marriage certificate of my 2xG GF Richard Todd gives William's occupation as "running fitter."
Please can someone describe what a "Running Fitter" does?

Also trying to locate a MARRIAGE Record for William TODD and Elizabeth WILSON circa 1800 in Sunderland.

No marriage found in FreeReg, although the likely children born to my GGG grandparents are:
- Robert Todd, born 17 Aug 1805, bapt 9 Aug 1807, Sunderland
- William Todd, born 7 Jul 1807, bapt 9 Aug 1807, Sunderland
(Family Search gives Wm Todd/Eliz Wilson as parents for these two, BUT FreeReg lists Wm Todd/Eliz WELSCH, and William as being from Houghton le Spring not Sunderland...)
- John Todd, b 18 Oct 1810, bapt 12 Jun 1811, Sunderland
- Lindsay Todd, born 9 May 1813, bapt 5 Sep 1813, Sunderland
- Richard Todd, born 14 Feb 1816, bapt 14 Mar 1817, Holy Trinity church Sunderland
- Elizabeth Todd, born 14 Oct 1818, Sunderland

Hoping someone can shed some light...