Pull cable release discharge heads use this mechanism. One or two separate cables can activate the head. The idea here is to make one cable easily accessible to the driver, while the other cable can be mounted so that it's easily accessed by someone else (for example, the passenger). The handle end of the cable is just like this. It's equipped with a safety pin. Obviously, the idea is to pull the safety pin before you race, then re-install it when the car is in the pits. Mounting of the cable is relatively simple. Some folks mount the handle right in the dash, while others simply build a bracket to hold it in place. Just remember to keep the handle in a spot that's accessible when you're belted in the car.