GURPSよろず

Cross Parry
If you have two ready melee weapons, you can commit both to a single parry. This is useful when your opponent has a two-handed weapon or one that’s so powerful or heavy that a one-handed parry would be risky. It often involves crossing weapons in an effort to catch the attacker’s weapon between them, which is why it’s called a Cross Parry.
To attempt a Cross Parry, both hands must be able to parry. Work out what your Parry would be with either hand, applying all the usual modifiers – for weapon type (e.g., -1 if using a knife), number of previous parries with that weapon, and so on. Your Parry is the better of the two modified scores, +2 for the extra support.
For the purpose of Parrying Heavy Weapons (p. B376), treat this exactly as if it were a parry with a two-handed weapon that weighs as much as the two weapons combined. Effective quality is that of the lowest-quality weapon. If the rules indicate that a weapon breaks, it’s the lighter of the two; if they weigh the same, roll randomly. Remember that two-handed weapons can parry things that weigh up to twice BL without being swept aside.

Example: A 2-lb. shortsword is normally susceptible to breakage against weapons that weigh 6 lbs. or more. Being one-handed, a weapon that weighs more than the user’s BL will sweep it aside. Crossed with a 1-lb. large knife, total weight would be 3 lbs. It would take a 9-lb. or heavier weapon to cause breakage – and if something did break, it would be the knife, not the expensive sword. Furthermore, this would let the defender parry weapons weighing up to 2×BL.

A Cross Parry is always legal against a flail weapon or a kusari, even if it involves two fencing weapons. Apply the usual penalty for parrying such a weapon to the final Parry score. If you parry a kusari, the wielder may attempt a free Entangle as usual (p. B406), with success binding both of your weapons.
The down side to a Cross Parry is that it ties up both weapons in a way that prevents you from using either for any further parries this turn. In addition, if you critically miss, the Critical Miss Table results affect both weapons!
Supported Parry: If you have a ready melee weapon and an empty hand, and both can parry, you can put your hand on your weapon to support it as you parry. This simply adds +1 to your Parry with the weapon and lets you parry as if you had a two-handed weapon. No other benefits apply. You cannot use either hand to parry again this turn.