I usually carry mine with me as I don't trust leaving it anywhere. However, when I have locked it up, I use the strap from my Kreiga with a carribeaner attached to the loop holes on the helmet strap to hold the helmet up. Then I run a bike lock cable through the visor hole. If someone wants it, they will get it, but it will be difficult. I lock it up to the rear seat grab. Can also put it on the mirror or bar end and lock it to the bars too. I would think if you have that much crime where you leave your lid on your bike and need something more than a cable through the visor, I would be carrying that biotch with me all the time! I have never seen a helmet extender through the ratchet.
Keep the rubber side down!