Watch winders are mechanical devices that keep an automatic or self-winding watch operating smoothly. Certain types of timepieces do not need to be wound by turning a dial because they wind themselves when they are strapped to an arm that is swinging and twisting all day long. Winders are able to simulate that natural motion for those who don't wear their watch everyday.
The internal parts of automatic watches are designed to follow the pull of gravity. They don't have gears that must be wound with a spring, but instead, their tiny weights get pulled by gravity as the wearer moves and swings his arm. Little by little, these weights are twisting around both clockwise and counter-clockwise, until the watch is wound up. This type is considered automatic or self-winding, as opposed to quartz, kinetic, or mechanical watches.
People who own fancy, collectible, beloved, or merely sufficient self-winding watches may want to invest in a winder. Not only do these devices keep the timepiece accurate even when it's not being worn, they probably extend its overall life by keeping parts lubricated and moving. By advancing the mainspring, it gently and continually winds the watch, yet prevents it from ever being "overwound." Another mechanism inside most watches will disengage after the gears have been fully powered.
Some of these devices are as decorative and elaborate as the timepieces that they hold. They may resemble cubes of polished and inlaid wood. Others have a glass top as a window to see the watch as it rotates, doubling as a display case. This is especially helpful when a person owns several watches and wants to keep them in view, away from dust, but protected like jewelry. The handle that holds the actual watch should be adjustable, so it can hold bands of different diameters.
Batteries power most watch winders, but some larger models use an AC adapter that plugs into the wall. Since they include a small motor, they may make a low hum, so owners may want to keep the box on a dresser or in a drawer rather than at a beside. A quality model will wind your watch counter- and clockwise, since the timepiece is designed to turn in both directions. They'll handle anywhere from one to eight watches, to cover a person's basic needs or display an entire collection.