Rather than armour giving "armour points" that reduce incoming damage, armour in Guild Dogs adds its value to a defender's DEX/STR statistic when being attacked. A Guild Dog wearing Light Armour (+2) with a STR of 12 would attempt to roll under 14 when defending. If a piece of armour prevented a Guild Dog taking damage (rolling above their DEX/STR, but below the armored DEX/STR value), they must check if it falls apart at the end of combat. Each type of armour has a usage die, rolling a 1 or 2 at the end of combat will reduce the armour's usage die by 1. Roll a 1 or 2 on a d4 means the armour is destroyed.
Light: 2 (d4 usage die)
Leather: 3, requires medium armour ability but can be used for sneaky activities (d6 usage die)
Medium, Heavy armour and shields are all metallic and noisy, inhibiting sneakiness.
Medium: 4 (d6 usage die)
Heavy: 6 (d8 usage die)
Shield: 1 (d4 usage die)
HD Creature's AC and Attack Bonus:
HD creature's AC is added to the attack test/roll of a PC (as well as their HD above the attacking player for the Powerful Opponents rule). This is to allow lower HD foes to be a little tougher/varied. HD creatures never have their armour tested to see if it falls apart, so the mechanical bonus is slightly less than PC armour. The rules for working out HD creature's armour listed in The Black Hack are no longer used.
HD Creature's Armour values:
Light Armor: +1
Medium Armor: +3
Heavy Armour: +5
Additionally, HD creatures a can have a bonus to attack, reflecting a number added to a PC’s DEX/STR test when defending.