mainsail boom preventer
Rigging a boom preventer will allow you to sail a true downwind course without a constant worry about crew safety. i also use it to pin the boom in its preferred position in light winds with. Rigging a boom preventer on an offshore sailboat the easy way.. Another form of preventer is the boom brake, which, when sailing downwind, can also be used to jibe the mainsail in a slow, measured action.the brake usually rides on a line running perpendicular to, and below the boom. when the boom brake is actuated, friction on the line either works as a preventer (stops the boom from moving in the direction that would slacken the main sheet), or slows the. 
mainsail boom preventer Proper boom preventer system, click image to link to sail magazine’s article on preventers. the boom preventer is a more traditional, highly effective method that can, if rigged properly, leave your deck clutter free. the preventer, unlike the boom brake, is to be rigged to the very outboard end of the boom via a pad eye and pendant(see diagram)..
