In mk9 I’m not exactly sure what it is but could someone explain it, and how you do it
If you switch between a high block and a low block within a couple frames of a low/mid connecting, your character will block the attack but will not change guard stance. This can be useful to remain standing while blocking lows, as standing block has less recovery and is generally less vulnerable.
^Stand blocking makes your hitbox more vertical, too.
But still watch out for throws if you fuzzy guard.