Players line up one behind the other rather than spread out. On a baseline inbounds that usually means all four in a single file in front of the rim. On a sideline inbounds or in the half court it more often means two pairs, one on each lane line, with the inside player screening and the outside player coming off.
Why coaches use it
A defender guarding a player in a stack cannot watch the ball and his man at the same time. He has to pick one, and whichever he picks, the cut goes the other way. That is the entire idea, and it is why stacks produce more lobs than any other inbounds alignment.
A stack also hides the play. Four players in a line give the defense no information about where anyone is going until the first man moves, and by then the second man is already using a screen.
The risk is congestion. Everybody is standing in the same square meter, so a cut that starts late runs into a teammate. Stacks need the first two cutters to leave on time more than they need anything else.
What comes out of it
- Peel to the corners. The front two break out to the corners and take their defenders out of the lane, which empties everything behind them.
- Screen the screener for a lob. One player screens another out to the top, then slips straight down the middle.
- Double pop. Both inside players screen and both outside players come up the sidelines at once, so the passer has two catches on the same count.
- A hammer. Break the stack to the far wing, drive the baseline, and flare a shooter to the opposite corner.
- A duck-in. Whichever screener is left alone inside seals and goes for the easier two.