As a reaction, which you use when you make a skill check or a saving throw to avoid being pushed, knocked prone, or grappled, you can sturdily position yourself. You make the roll with advantage. You can do so after the roll but before any effects of the roll occur.

If the roll already has advantage or disadvantage, you cannot apply another instance of advantage or disadvantage and you must use this before the roll to cancel out any advantage or disadvantage.