Scooby, the captive system is the updated ball for the mast step, with the pin which is used to hold the new mast base onto the ball while stepping the mast. It's common practice to always remove the pin while sailing; I rivet an eyestrap to my mainbeam near the mast step to store it, so if the mast does come down on the water, the "captive system" will be available and there might maybe be a chance of stepping it again.
Sail fast