to hand something to a strong man for opening or to be moved. It implies that men are strong. It is most often used by a female to get something done that she isn't able to do herself, although has been used by smaller men to solicite help from larger, stronger men.
women might say:
Hey, could you man this open for me?
Could you man this over there for me?
a man might say to another man:
Could you help me man this over there?
(especially if it were too heavy for one person)
the male version of the word cunt. A cock knocker is a male who needs to be called the worst word you can come up with. He is the kind of man that if he were a woman you would call a cunt. He is the kind of person that will relentlessly take the wind out of you, deliberately sabotage you, and sometimes even seems to enjoy being hated.
My professor is such a cock knocker! He said that all the girls in the class may as well drop because they won't pass anyway! GRRRR... I loath that mo-fo!