M_Boats: M-17 questions round 2

Now for a couple questions regarding boom hardware. I'll attach a few photos. When I got the boat, there was this short line tied at the rear of the boom. I've been using it to support the boom when the sail is not up (by tying it to the ring at the split in the backstay). Is this same line used to tension the sail foot by pulling it back? Or maybe some of the hardware on the boom is used. I'll attach as few photos of the boom showing both sides. Can anyone tell me what the hardware is for? Thanks very much for any input! -Gerry