Before the big sets the ball screen, a teammate screens the big’s defender from above. The big sprints into the pick with a step on his man, and the ball screen happens before that defender has caught up.
Why coaches use it
Every aggressive ball-screen coverage depends on the screener’s defender being in position when the screen is set. A hedge needs him out above the screen on time. A switch needs him level with it. A hard hedge needs him there early and moving.
The ram takes that away. Screen him once and he is a step behind for the rest of the action, which means his hedge arrives late or his switch is a mismatch that never got organized.
It is also easy to install. The screening angle is the only thing to teach: the rammer comes from above, sets his feet, and the big goes shoulder to shoulder off him. There is no timing trick beyond that.
How it is guarded
Two workable answers, and neither is free.
- Switch the ram. Now a different defender is guarding the screener, usually a smaller one, and he is the man who has to hedge or switch the ball screen. The offense will look for that mismatch on the roll.
- Go under the ram. The big’s defender takes the short way and tries to beat the screener to the spot. It works if he is quick, and it fails badly if he is not.
Either way, somebody has to call the ram out early. A defense that only recognizes the ball screen is guarding the second half of an action that was decided in the first half.