Specifications of the lockstations:

Detached lockstation: One lock with a lift of 2.6 m (8.5 feet)
Combined lockstation*: One lock with a lift of 7.6 m (25.6 feet)
Old Slys lockstation: Two locks (in flight) with a combined lift of 4.9 m (16.1 feet)

* The present day Combined Lock was built in 1972-74, replacing the original Smiths Falls Combined Locks, a flight of 3 locks, which still exists, non-operational, just to the south of the new lock.

The Construction of the lockstation

The contractors for the original Smiths Falls Combined and Detached locks were Rykert, Simpson and Company (a.k.a. Rykert, Simpson and Adams). They abandoned their contract in January 1831 and Bell, Richardson & Co., the contractors for Edmunds and Old Slys, took over.

The contractor for Old Slys was Bell, Richardson & Co.

An 11 m (36 foot) drop in less than 400 m (1/4 mile) posed an obstacle to navigation at Smiths Falls. A natural depression to the south of the river was used to place a flight of three locks, known as the Combined Locks. The natural course of the river was dammed to create a basin upstream of the locks. At the upper end of the basin a fourth (Detached) lock was constructed.

This canal town is named for Thomas Smyth, a Loyalist who in 1786 was granted four hundred acres in what is present-day Smiths Falls. At the time of canal construction a small settlement had been established around a mill operated by a local named Abel Russell Ward. Colonel By ordered the removal of Ward's mill to make way for the canal. He settled with Ward for £1,500, one of the largest claims made by mill owners on the canal.

The disruption of industry caused by the building of the canal was only temporary, and Smiths Falls grew rapidly following construction. An article in Smith's Gazetteer in 1846 described the town as a "flourishing little village pleasantly situated on the Rideau River and on the Canal, fourteen miles from Perth. It contains about 700 inhabitants.

Some 1.6 km (1 mile) below the Combined lockstation is a flight of two locks called Old Slys lockstation. This station is named for the original settler at this location, William Sly. A dam and waste water weir control water levels upstream of the locks.

Structures of the lockstations

New Combined Lock: Between 1972-74, a new single electric hydraulic lock was built at Combined lockstation just to the north of the old flight of three hand-operated locks. This new deeper single lock was required to allow boat traffic to clear a new low-level fixed bridge that was built to replace the swing bridge that used to cross the channel above the upper lock of the original Combined locks.

Lockmaster’s Houses: Defensible lockmasters' houses were built at all three stations in Smiths Falls. The house at Old Slys was built in 1838 and the houses at Combined and Detached around 1842. Only the house at original Combined has a second storey, which was added late in the 19th century. The defensible lockmaster's house at Detached lockstation was torn down in 1894. It was replaced by a two storey brick building, which was removed in 1973. The defensible lockmaster's house at Old Slys lockstation was torn down in 1965 with a new lock office built on its foundations.

Dams: The original 7 m (23 foot) high stone arch dam at Smiths Falls is now mostly buried, the area, part of the former channel of the Rideau River, was backfilled in the mid-20th century. Today the exposed upper portion of the dam is used as a retaining wall for the parking lot below the water tower.

At Old Sly’s, the area below the 6.1m (21 foot) high canal dam, and above the railway bridge was backfilled the mid-20th century leaving only the top of the dam exposed.