Restored by Cotswold Canals Trust. Formerly known as Lower Nassfield Lock, this was an original lock of the Stroudwater, designed to cater for Severn trows and was about 16 foot wide and 68 feet long. The lock had a rise of 7 feet 5 inches. It was the second to top lock of the five in the Eastington flight, built in 1777.
Its present name is due to the fact that it was originally built at the wrong level. Unlike the other Stroudwater locks, this chamber is mainly lined in ashlared stone, with stone capping and stone quoins to the gate recesses.
The mouth and the tail sections are also lined mainly in stone. There are paired vertical sluices on either side of the approach, or mouth, of the lock above the top gates.