ok well parry is a response action so you pay a dark symmitry point to use it and it then becomes an opposed test against the attackers close combat skill both at D1whoever gets the most momentum wins the test if its a draw the charcter with the higher expertese wins
Right, the Parry X weapon quality works as follows - once you make a Parry response action, for the rest of the round (until the start of your next turn), you gain additional Soak against melee attacks - a number of dice of Soak equal to the Parry quality's rating (the X), representing the character continuing to defend themselves (as you only get one Response Action per round).
So, a character with a weapon with Parry 2 would roll two combat dice (as if he were in light cover, essentially) and add the total rolled to his Soak whenever he was hit with a melee attack.
Full Defence X works the same way, only the bonus Soak also applies to ranged attacks as well, as Full Defence allows you to parry ranged attacks as well as close combat ones.
Game Development - 2D20 System
System Design - Star Trek Adventures