A broken cannon base is used when repairing dwarf multicannons within the Artisans Workshop. It can be taken from the cannon base desk within the repair room. The cogs need to be removed from it, leaving you with an empty cannon base and 10 broken cannon cogs. The cogs should be repaired and re-added to the base, giving the repaired cannon base
This item cannot be taken outside of the repair area. It can be re-obtained from Isak if you have left the area after obtaining it.