Lock Ring Explanation

The o-ring in the lock ring provides a friction fit between the lock ring and the die.  Once you have the die adjusted to your satisfaction, hold the die with one hand and turn the lock ring down against the press frame (turret, tool head, etc.) finger tight.  This will be enough to hold the adjustment during the reloading process.  If you have to remove the die, loosen it by the lock ring.  When re-installing the die, tighten in down by the lock ring finger tight, and it will be in the same place as when it was removed.