Repairing equipment is possible during rest or back in civilization. Items with less than max durability but greater than 0 durability can be repaired. No check is necessary to repair the item if the PC is proficient in its use and has a forge or similar workstation.

Repairing a sundered item with improper tools, while not proficient, or while in a dangerous situation (such as a dungeon) requires an INT check with DC 10 + DUR attempted to be repaired (such as DC 11 for 1 DUR, DC 12 for 2 DUR, etc). Having the right “kit” grants advantage to this check. Each DUR repaired requires 1 SUP and 1 hour of labor, regardless if a check is made.