Originally Posted by mx_599
What do you mean to remove it...but not to replace it?

I guess it is a free wheel?? Off a MTB. You mean free wheel as opposed to locking as in a rear brake skid??
Is the Park Tool mentioned above the appropriate one? Sorry, I am new to much of bike terminology.
Whip it good -Devo

Take your rear wheel in hand. Spin the casette. Whirr, clickity clickity. That's the action of a free wheel hub. Cool right? The direction that the casette spins is the direction that the lock ring needs to spin to come off. So the whip holds the casette while you wrench the lock ring off. See?
You don't need the whip to put it back on because the casette engages in the forward direction. IOW, it doesn't free wheel in both directions. Therefore, you can use the leverage of the whole wheel against the torque of the wrench to replace the lock ring. Easy. Right?