Some sports equipment items that begin with the letter O are oars, outrigger skis, and overgrips. These items are used in the sports of rowing, paraskiing and tennis, respectively.
Oars are used in competitive rowing to propel the boat through the water. Each oar is attached to the boat by a oarlock, which allows the oarsman to pull on the oar handle and use leverage to move the oar blade through the water with increased force. The amount of leverage is determined by the blade size, the overall oar length, and the inboard length, which is the amount of the oar that is inside of the rowlock.
Outrigger skis are designed for skiers who have lost the use of one or both legs. By sitting atop a sled-like structure on one single ski, the skier maintains balance by using poles, or crutches, which also have skis attached to them. This type of set up is named for its resemblance to an outrigger canoe, which is yet another piece of equipment that begins with the letter O.
An overgrip is used in tennis and is, basically, a type of padded tape that is wrapped around the tennis racquet handle. Its purpose is to make the handle easier to grip by adding thickness and tackiness and by absorbing perspiration. The overgrip can be wrapped in an overlapping fashion to provide extra thickness for players with very large hands. Overgrips are also used in other racquet sports such as badminton and squash.