1. complete (work)
knock off work (early)
As a verb, 'to knock off' means the same as 'clock off', to 'knock off work' or finish work for the day. This is an informal expression used in social and professional contexts.
2. a fake version of something else
a knock-off of the real thing
'A knock-off' (noun) is an imitation of the original or of a designer product or a counterfeit product. This expression can be used in social and professional contexts.