A drive gets into the paint and the lowest help-side defender steps in to stop the layup. The ball gets kicked to the corner, which is the man that helper just left. Instead of sprinting all the way back there himself, he closes out to the wing, and the defender above him drops down to the corner. Their two paths cross. That crossing is the X.
Why coaches use it
Because the direct recovery is a race the defense loses. The helper came from the corner to the rim; going back is the longest sprint on the floor, and the shooter only needs the ball to travel one pass. Trading assignments turns one impossible closeout into two hard but survivable ones.
It also keeps the biggest body at the rim. In most versions the man who helped stays inside for the rebound while the smaller defender takes the corner shooter, which is the matchup you want anyway.
The costs are real. Somebody is closing out long, so a shot fake beats him. And for a moment nobody is boxing anybody out, which is why teams that rotate well still give up second shots.
How to attack it
- Make the first help come from as far away as possible. The more ground the low man has to cover, the worse the rotation behind him.
- Attack the rotating defender, not the open man. He is closing out long and late. One dribble past him is a better shot than the catch-and-shoot you just created.
- Use the skip. Hammer is built for this: the drive pulls the low man in and the flare screen sends a shooter to the corner the rotation is trying to reach.
- Send the corner shooter through. If the corner is empty, there is nothing to rotate to, and the help has to come from a shooter at the arc instead.