Scope models that feature zero-stop functionality:
Dail the elevation and windage turret at your desired zeroing distance, 25,50,100 yards/meter.
Remove the turret cap by unscrewing the top stainless steel screw with a coin or cartridge case base.
Lossen the zero stop ring by all three set scews
Lower and rotate the zero stop clockwise until the ring extrusion hits the top-notch.
Tighten back all 3 set screws on the zero-stop ring
Install the turret to make the 0 position line up with the indicated center on the scope body.
Reinstall the top stainless steel screw.