A horns set, walked through option by option
Set plays
Five players, two elbows, two corners, and the three things that happen depending on how the defence reacts.
Horns is a starting shape rather than a single play. The ball handler stands at the top of the key. Two big players stand at the elbows, the corners of the free throw line, one on each side. The remaining two players stand in the corners of the court behind the three point line. From above, the arrangement looks like a pair of horns, which is where the name comes from.
The shape is used because it stretches the defence in two directions at once before anything happens. The two corner players occupy the defenders furthest from the basket. The two elbow players occupy the two biggest defenders in a spot where they cannot easily protect the rim. The area directly under the basket is empty, which is the point.
The first option is the simple one. One elbow player steps up and sets a ball screen. The handler comes off it, the screener rolls to the empty basket, and the other elbow player pops out to the arc behind the play. Now the defence has a driver, a roller and a shooter to account for, and it has to give up one of them. If the defence hedges hard at the ball, the roller is free. If it drops back, the handler has a pull-up jump shot from the free throw line.
The second option starts identically and finishes differently. The screener, instead of rolling, slips the screen: he turns and cuts to the rim a fraction before making contact, because he can see his defender preparing to step out. A slipped screen beats an aggressive defence and it is the standard answer when a team is trapping the ball handler.
The third option uses the far side. As the ball screen is set, the second elbow player does not pop. He turns and sets a flare screen for the corner player on his side, who runs up to the wing behind it. The defence has been pulled toward the ball, and the flare produces a catch and shoot from an angle where nobody is close.
What makes horns useful for a viewer is that it is easy to recognise and the options branch predictably. Once you spot the two players at the elbows and two in the corners, watch the defender guarding the screener. What he does, step out, drop back or switch, determines which of the three options the offence takes, and he has to decide before the ball gets there.