This harkens me back to a painful day on our Cal 36 'way back in the 1960s. On our way back into Alamitos Bay I was sitting at the tiller while when my dad tripped the mainsail halyard, but beforehand he'd forgotten to secure the topping lift. The boom crashed down right on the top of my head and it's a wonder I didn't get knocked out. But it hurt like hell; left a nice big knot right on top of my head. I noticed the topping lift was not hooked at the precise moment my dad tripped the halyard; no time to react. That was a new experience in pain.