These are some rules I use to help low-level player characters to survive a little longer, and also to help soak up some of that treasure that they are always carting around.
Players buy armor for their characters at character creation and then to upgrade it, but you never see them buying replacement armor or paying upkeep for what they have. Instead of coming up with a rule to reflect upkeep and maintenance costs, I thought to adapt the “Shields be Splintered” rule I've seen on various blogs and in old-school publications, though I've expanded it to cover all armor.
The same is true for weapon maintenance, and so I've tacked on a rule to allow weapons to fill the same role as well.
Sacrificing Shields & Armor
After a hit has been declared on a character by a melee attack, the player may decide to take the damage to his shield or armor instead of his hit points. This must be declared before damage is rolled, so the hit might be for 10 points or only 1, but will still have the same effect on shields and armor.
A wooden shield so struck is destroyed (all shields are assumed to be wooden unless specially purchased otherwise), while a metal shield is useless until repaired and counts as double encumbrance to carry around. Metal shields also have other benefits (see below).
Armor so struck is reduced in effectiveness by 2 AC ranks. (Leather Armor of AC 8 is rendered useless, Chain is reduced to AC7, and so forth) Armor so damaged counts as double encumbrance and imposes a -2 to all attack throws by the wearer until removed or repaired. Armor that still has a AC below 9 may take yet another hit, but then is rendered completely useless and cannot be repaired or worn effectively.
Missiles, Magical attacks and Breath Weapons are not affected by this rule.
A metal shield, however, may be used to halve damage from a breath weapon (except chlorine gas or lightning). This can be declared after a successful Save vs. Dragon Breath, and halves damage yet again. However, the shield is rendered useless afterwards. This defense may also be used against Fireball spells, but not against Lightning bolts.
If a character has elected to use the Parry option (see Advanced Editon Companion or Holmes Basic) to defend themselves, the player may elect to take a successful hit on his weapon. This breaks the weapon, rendering it useless until repaired or replaced. Magical weapons may take hits equal to their bonus without breaking, but are then rendered completely non-magical and will break on the next hit absorbed.