1790 - 1795
Double lock, constructed c.1792. Dressed limestone chamber walls with gate recesses, cast-iron mooring rings and dressed limestone coping. Timber mooring posts to south side of chamber. Replacement timber and mild steel lock gates with timber balance beams. Walls of lower chamber slope up to middle gate with flight of replacement stone steps. Recesses for stop gates to eastern end. Canal expands to west to provide mooring area.
The Royal Canal Company was established in 1789 to construct a canal to provide freight and passenger transport between Dublin and the River Shannon. Construction began with the laying of the first stone of the lock at Phibsborough (now the 5th lock) in 1790 and construction was completed to Ashtown by 1792. The chambers exhibit good quality stonework with attractive sloping edges to cope with the change in height between the lower and higher levels, a testament to the skill of the craftsmen involved. One of a number of double-chambered locks on this stretch of the canal it attests to the skill of the engineers employed by the company.