Les, knock-knocker are truly useful words-
That striker thing on doors (superceded by the electric bell) was called a knocker (door knocker).
A person who knocks on doors looking to sell something, or solicit a donation, is often called a 'knocker'.
In Australia a casual labourer may be called a knockabout.
Casual clothes are sometimes called knockabouts.
Knocker- a person of striking appearance, a 'stunner'.
In mines, a goblin, etc., who is heard knocking on the walls.
At the end of the 19th C., 'up to the knocker' was slang for 'up to the mark'.

There are undoubtedly more. Indeed confusing to a furriner.