Understanding the Fly Zone in the 4x100m Relay

"DARREN STORR: Hi. My name is Darren Storr. On behalf of Expert Village, I'm showing you guys how to run the 4 x 100 relay. All right, this is my teammate, Louis Young. He's going to help me demonstrate some of the baton relay exchanges throughout the zones. Basically, you cannot hand the baton off through the fly zone. That's the point where the runners or the runner accelerate. You have to use the [SOUNDS LIKE] diamond, 20 meters after and before--before you get to your main point. So he's going to be handing off right in the middle up to here. So 10 meters before and 10 meters after. But he cannot hand it within the fly zone, the exchange zone, we call it, 'cause the runner needs time to accelerate before handing or taking the stick off. Stick. Stick."