
You are behind them with hooks or a body lock. Keep the seat belt tight and hunt the choke.
Taking the back is the goal of many BJJ game plans. You are behind them with your hooks or a body triangle around their hips and a seat belt grip across their chest. You score 4 points, and they can't see you or reach you easily. The rear naked choke, the bow and arrow choke and armbars all come from here.
Control comes before the finish. Keep your chest glued to their back and your head beside theirs, and follow them when they slide to the mat. Hunt the neck patiently: if they defend the choke, switch to the other side or attack the arm.