Tarmonbarry Lock has been re-opened to boat users after being closed for several weeks for repairs.
Emergency works began on the structure at the end of February in an effort prevent the possibility of the gate collapsing into the lock, after significant damage had been spotted in previous months.
The gates are also used to control the water levels on the Shannon and it had been intended to re-open them at the end of April.
Further damage identified when the works began though meant the lock had to remain closed until recent days.
Waterways Ireland says some restrictions in the operation of the gates remain in place and boat users are advised to take extra care when approaching the lock.