Grappling

Direct physical contact with an opponent involving wrestling or an attempting to relieve them of a weapon.

The Book of War says:

3.6.1. Combatants may initiate Grapples with opponents according to the following rules.
3.6.1.1. A Combatant wearing no Armor may Grapple all opponents.
3.6.1.2. A Combatant wearing Leather Armor may Grapple any Armored opponent, but not unarmored opponents.
3.6.1.3. A Combatant wearing Chain Armor may Grapple opponents wearing Chain or Plate Armor.
3.6.1.4. A Combatant wearing plate Armor may not initiate a Grapple.
3.6.2. A Combatant wearing plastic safety equipment is treated as leather Armor for grappling purposes only.
3.6.3. No throws, unarmed strikes, or joint/nerve holds.
3.6.4. Combatants with Missile Weapons (Type 4, bow/arrows) may not initiate Grapples or be Grappled.