Spark Plug Advice Needed

What in the world is a transfer screw, speed screw?? Never heard of either of these until now
The transfer slot is down inside the primary throttle bore, on the front side, and is the primary source of fuel delivery from idle to roughly 30% throttle opening, (I'm guessing) when the Mainjet comes on line.
At idle, transfer-slot fuel is augmented by fuel coming from the Mixture screw ports.