He is talking about the brass piece on each carb that sticks out about 1/16th of an inch, maybe not even on the inside of the carbs along the slide walls. They are there to keep the slide from spinning around in the carb so that the slanted part of the slide will stay facing the rear of the carb (towards the air filter). I'm pretty sure this is what he is talking about...
thats what he is talking about.