HGd10PHB - Special Attacks - Parry

Parrying is a physical melee move that is used against other physical melee attacks. To make a successful parry, the defender must:
* Have a Response Action available.
* Make a successful melee Attack roll equal to or higher than the Attack they are defending against.
* The Parry consumes the Standard Action of the one parrying but they may still use a Secondary Action or Move regularly.
* If the Parry roll is at least 10 higher than the incoming Attack roll, and the defender knows the Riposte move, they may make a Riposte attempt.
Note, certain weapons give a bonus on Parry attempts including certain polearms and swordbreakers.
Sais are capable of two independent parries in a single Response time frame.