Drawing of a verge escapement "(bottom)" and balance wheel "(top)" from an early pocketwatch, in an 1820 encyclopedia. The verge escapement, the oldest mechanical escapement, was used from the 13th century, and was the first escapement used in clocks and watches. It consisted of a vertical rod, the "verge", with angled flat plates called "pallets" "(e,f)" attached. The pallets are pushed by the teeth projecting from a vertical wheel "(c,d)", turning the balance wheel alternately clockwise and counterclockwise, against the restoring force of the balance spring "i". The verge was replaced by better escapements beginning around 1700 but verge watches continued to be made until the mid 1800s.