Here are some pictures of my preventer. It’s permanently rigged. A short line runs from the aft end of the boom to the aft main sheet bail. This line has two eye splices one us used to attach it at the aft end of the boom using a luggage tag knot. The other end is temporarily attached the the aft main shear bail when it’s stowed. On deck their is a clutch on the track through which runs a line to a turning block and the line is brought back to the gate stanchion where it is stowed using a snap shackle.
When deployed the snap shackle is used to attach the line to the line on the boom. Having the preventer line in two pieces like this allows one to attach the preventer when the boom is out over the side without having to lean over the lifelines.