Thanks Peter. Hawk20s come with a cunningly designed aluminium pole that fits in a socket to support the boom end and immobilise it. It stops the boom beaning you when the boat rocks with the main down, and means you can safely leave the boat in the water with the mainsail secured on the boom under a sail cover. Because the boom is then secured by gravity and a lightly tensioned mainsheet (just enough so the boom end can't jump out of the crutch), it relieves stress on the rig when parked up, rather than adding stress and wear as the usual kicker/mainsheet/topping lift boom securing arrangement does on many yachts. I expect a variation on this could be rigged or bodged to fit a BC20 or BR.