A FIRE ON SUNDAY at Twin City Lock and Key that took crews nearly five hours to extinguish totaled the business, but owner Chris Cunha said Monday that he plans to rebuild after an insurance appraisal. “We lost everything,” Cunha said, “but we’ll make it through.” Cunha confirmed Monday that a welding accident caused the fire, which started while his son was working on a truck on a lift inside the building. Cunha said the fire started inside the vehicle and quickly spread through the whole building, which is across the street from the Wiscasset Airport at 137 Chewonki Neck Road.