Locking adjustment knob

An adjustment apparatus for a sighting device, the adjustment apparatus comprising:

• an adjustment mechanism mountable to the sighting device, the adjustment mechanism configured to adjust a setting of the sighting device;
• an adjustment knob operatively coupled to the adjustment mechanism, wherein rotation of the adjustment knob about a rotational axis drives the adjustment mechanism and adjusts the setting of the sighting device;
• and
• a lock mechanism including:
• a first lock element fixed relative to the sighting device;
• and
• a second lock element selectively movable relative to the first lock element, wherein the first and second lock elements engage one another in a locked position to restrain rotation of the adjustment knob about the rotational axis, and wherein the first and second lock elements are disengaged in an unlocked position to allow the adjustment knob to be rotated about the rotational axis.