Post O4 with a ball steps out to set a sidescreen (back to the elbow, inside the arc), then opens hard, gets to the 21 position at about 12 feet, and reads from there. He can go to the rim and sit and seal (in a game situation, defenders switch and he has a mismatch), or he can step out towards the corner (he can shoot, or defenders switch and the dribbler has the mismatch). He triangles perimeter or post.
His options are to shoot on the roll (catch on the dribbler's first dribble in a game situation), from the 21 position (second dribble), stepping out or sealing (third dribble). When sealing, a game pass would come from the wing or high post.