Daniel Defense's One O'clock Offset Rail (Rock Lock) is optimized for mounting miniature red dot optics in the O'clock (right-hand) or 11 O'clock (left-hand) positions for quick, non-magnified, transitions when employing magnified primary optics on Rifles with MIL-STD-1913 rails. The geometry allows for zero cheek-weld shift during the transition. This facilitates very fast transitions from magnified to non-magnified optics, and back. The O'clock Offset Rail can also be used to mount variety of lights or other accessories that mount to MIL-STD-1913 rail. By flipping the part upside-down, one can mount light in good position for use with vertical foregrip.