A can opener (also known as a tin opener) is a device used to open metal cans. Although preservation of food using tin cans had been practiced since at least 1772 in the Netherlands, the first can openers were patented only in 1855 in England and in 1858 in the United States. Those openers were basically variations of a knife, and the 1855 design is still being produced. The first opener employing a now familiar sharp rotating wheel, which runs around the can's rim cutting the lid, was invented in 1870, but was difficult to operate. A breakthrough came in 1925 when a second, serrated wheel was added to hold the cutting wheel on the rim. This easy to use design has become one of the most popular can opener models.