You use a Medium Weapon to cripple a limb or knock out a lightly-armored target.
When you strike an enemy with a Medium Weapon in a part of their body that is not protected by Medium Armor or Heavy Armor, you can spend 1 Valor Point and call out Cleave to inflict the Maimed condition on one of their limbs or reduce their Hit Points to 0, based on that call’s description.