Sea lock at Clachnaharry, Invernes, 1838.

Canal lock gates, 19th century.

Locks on the Ellesmere and Chester Canal, 1838.

'Locke adder', 1901. Locke adder calculatin

Cast iron swivel bridge at St Katharine's Docks, 1838.

Construction of the Panama Canal, Panama, 1912.

Scottish traditional wooden lock, 1740-1760.

Steel lock, 18th century.

Bras puzzle combination lock, 18th century.

German steel chest lock with key, 17th century.

Lock plate, French.

Lock, Norwegian, 1780.