The pin point of the needle goes into the cup on the bottom of the heim joint. You just hold pressue agaainst it while you pump the grease gun. The needle is hollow of course, but tapered down on the like a knitting needle with a hole in it.
They're a little messy to use, but there's no ugly zerk fitting sticking out. I'm not sure in this case though, there's plenty of room for a zerk, maybe just the visual of no fitting appealed to them.
