This leads to the following other slang terms:
The castle--the girl in question
The king--the girl's boyfriend (as in "the king is in the castle"
To storm the castle--to hit on the girl, not seriously but just to antagonize the porticullis
Also: boiling oil, trebuchet, battering ram, protracted seige, etc. can be used allegorically to describe specific situations that arise in this setup.
In this instance (and many others) Clint was being a porticullis.