
My boom brake is a Wichard product, I hang the friction device just past mid-boom. The control line clips to a car on the port side genoa track, routes through the friction device and down to a turning block clipped to the starboard genoa track then back to the aft cleat. The more loops through the “figure 8” the more friction. When sailing I will “set” the device by pulling any slack out of the non-working side of the control line while standing in the companion way with the center window open.
Location of the friction device is per your convenience - remember a boom brake doesn’t stop the boom, it simply slows it to a manageable rate of swing. I can put a newbie at the wheel on a downwind run and take a nap knowing that we won’t get knocked down.
An improvement would be a dedicated control line cleat or clutch on the cockpit combing close to the wheel. (I have a photo but it isn’t loading to the forum, will try later).
Oh, and don’t attach the control line to your cabin-top handrails like that picture on the eBay website!