The rings are standard apparatus used in male gymnastics. They consist of two rings, typically made of wood (competition), or some other material (http://www.ringtraining.com ring training). They are also known as the still rings, due to the goal of optimal performance of the male gymnast, which is to keep the rings as still as possible during a routine. The use of gymnastics rings is not limited to competitive sport, however; many people use rings to enhance conditioning programs.
Aleksei Nemov on Still Rings, 2000 Olympics.
Early gymnastic programs (developed heavily in Germany in the early 19th century) included much of the modern apparatus now used in men's international competition, except for the Still Rings. The rings were developed by Friedrich Ludwig Jahn, who is often referred to as the "Father of Modern Gymnastics". They were originally called "Roman Rings" due to their origins in Italy, which date back possibly two thousand years, but Jahn,  did not initially include them in his program. 
Adolf Spieß introduced what he referred to as Ringeschwebel in 1842 (he described them as such in his Turnlehre, or "gymnastics lesson"), originally introduced as a swinging apparatus, known as the "flying rings." These were triangular shaped. At some later date circular rings replaced the original version. Since then rings have been made of metal, leather-covered metal, rubber-covered metal, and finally the wood laminated rings used today. Initially, German gymnasts experienced difficulty with the rings; much of the development of the rings took place in Roman and Benelux States.  Eventually, the flying rings were removed from collegiate circuits in the 1960s. Frank Snay, of the United States Naval Academy, was the last NCAA winner of the flying rings in 1961.  They appeared for the first time in the Olympic Games in 1924 (Paris, France, VIII Olympic Games). 
The still rings make up one of six components in Men's Artistic Gymnastics. Exercises on rings consists of swing, strength and hold elements. Generally, gymnasts are required to fulfill various requirements, such as a swing to handstand, a static strength hold, and an aerial dismount. More veteran gymnasts will often include more than one strength element, swinging into hold positions or executing different holds consecutively. Some of the more popular techniques include the Iron Cross, Maltese Cross, and the Inverted Cross. Moves on the still rings are regulated by the Code of Points.
General Exercise Use
Many people choose to incorporate use of the rings into their normal exercise programs, due to the way the rings enhance the effectiveness of many exercises. Many popular ring exercises, such as pushups, muscle-ups, pullups, dips, and variations of all types, don't require the dexterity of more advanced gymnastics techniques, which broadens the appeal to the general populace. When the versatility of exercise selection is combined with the versatility of use (they can be suspended from just about anywhere, and some types come equipped with adjustable straps), they become a valuable asset to gym or home enthusiast.
Measures of the apparatus are published by the Fédération Internationale de Gymnastique in the Apparatus Norms brochure.
- Point of suspension 5.75 meters above floor
- Height of rings 2.75 meters (including about 20 cm landing mats)
- Distance between the rings 50 cm
- Inside Diameter of the rings 18 cm
- Total Diameter of the rings 23.6 cm (Thickness 28 mm)
- Ring Training-A website dedicated to ring training. Rings can be purchased here.
- Fitstream- Gymnastics rings articles, exercises and equipment.
- Drills and Skills Rings Page
- The 2006 Code of Points
- Apparatus description at the FIG website
- How to Make Your Own Rings
- unknown (n.d.). Climbing and Gymnastics, A Historical Association. HickokSports.com. Retrieved on July 21, 2008.
- various (n.d.). Rings. Encyclopedia Britannica. Retrieved on July 21, 2008.
- Gill, John (n.d.). Climbing and Gymnastics, A Historical Association. JohnGill.net. Retrieved on July 21, 2008.
- unknown (n.d.). Artistic Gymnastics, History of Rings. GymMedia.com. Retrieved on July 21, 2008.
- various (n.d.). Flying Rings. Wikipedia. Retrieved on July 21, 2008.