When a weapon, shield, or suit of armor receives wear and tear in combat, it's considered degraded. Degradation occurs when a weapon or shield is used to parry and the player rolls a Critical Failure. Similarly, a suit of armor is degraded when the player rolls a Critical Failure on the Guard Roll.
When a piece of equipment becomes degraded, it takes a −1 penalty to its bonus (i.e. a weapon or shield will receive −1 to attack and parry, meanwhile armor will receive −1 to the Guard Roll). Equipment will continue to degrade in combat, incurring further stacked penalties. If the amount of degradation exceeds the bonus the equipment confers, it falls apart and is ruined.
Fortunately, a character can have any of their equipment repaired by a skilled artisan (perhaps even herself, given the facilities and resources). To repair one level of degradation, the cost is a fraction of the cost of the item. To calculate the repair cost, divide the purchase price by the equipment bonus. For example, as detailed in the Equipment chapter, leather armor costs 300𝕤 and it provides 3 points of armor bonus. The repair cost for each level of degradation on a suit of leather armor would therefore be 100𝕤.
Bows, crossbows, and firearms are special cases. These weapons only have a single point of degradation. If they're used to parry and the player rolls a Critical Failure, the bowstring is cut or the mechanism becomes jammed. Bows are easy and inexpensive to re-string, however crossbows and firearms are complex devices which require specialized repair. Repairing a degraded firearm or crossbow incurs a cost of 20% of the purchase price.