I also gots me one of these:
http://cgi.ebay.com/ebaymotors/Indian-moto...=item45ee990a5c
I use it on my rails disc brakes, fits right in the disk holes and won't allow it to roll and also alarms if someone tries to cut the cable and roll it.
BTW, that is a smokin deal on that auction link....I believe I paid like 60.00 or more at carter PS