To add to this - the autoblocking devices seem to lock up pretty easily, even if the rope is newer and more supple than an old rope. I put a second biner through the device to keep it from locking up as easily (here come the naysayers!!!) and I haven't had a problem even with a rope as stiff as a cable, and Jim's rope is nearly that! And no, the xtra biner hasn't kept the device from operating in this mode safely!