On the lower end of the lock, crews must work across the girder in wetter conditions, wearing life vests for safety. The rigger or signalman on the barge keeps a close eye on the installation. He uses both a headset and hand signals to indicate “stop” to the crane operator as the second needle is properly fitted in the slot. It takes a significant amount of experience and expertise for a crane operator to maneuver and place each needle down into the small slot, fitting them close enough together that the two pieces can be sealed together with a narrow black seal, visible on the left side of the second needle.