Four players stand along the baseline, usually two on the blocks and two in the corners, with one player up top. Everything is below the free-throw line, so the top of the floor is completely empty.
Why coaches use it
It is the easiest alignment in basketball to line up in and the hardest one to switch, because all four defenders are standing next to each other facing the same direction and none of them can see the ball and his own man at the same time.
That is why it shows up most often on baseline out-of-bounds plays. Four across the floor facing the inbounder means every screening angle along the baseline is available, and one cut behind the line of defenders produces a layup before anybody has turned around.
It is also useful as a press-attack shape. Spreading four players to the baseline and corners forces a pressing team to cover the full width of the floor, and the empty top of the key is where a guard can catch and turn without being trapped.
Used in the half court it is a decoy more than an offense. There is nothing above the free-throw line to draw the defense out, so a good team will simply pack the paint. Most coaches treat 1-4 low as a starting picture and get out of it within two seconds.
What comes out of it
- A baseline runner. One player runs behind the rim and comes off a stagger on the far side while his man fights through traffic.
- Back screens. The man guarding up the line gets screened and the cutter arrives at the front of the rim.
- A lob. Nobody in a line facing the ball is watching the rim.
- A corner spot-up. Clear two players out and the inbounds pass becomes a catch-and-shoot.
- A seal and duck-in on the weak side, once the defense has committed to the first cut.