Side Focus
A parallax adjustment knob mounted on the left side of the scope, opposite the windage turret. Replaces the older adjustable objective layout.
Side focus is more ergonomic than AO. You can adjust parallax without breaking your shooting position or reaching to the front of the scope. Most precision scopes from the last 15 years use this design.
The knob is usually marked with distance reference values (50, 100, 200, 400, 600, 1000, ∞). Set it to match the target distance and parallax disappears.