Racquetball is a racquet sport and a team sport played with a hollow rubber ball on an indoor or outdoor court. Joseph Sobek invented the modern sport of racquetball in 1950, adding a stringed racquet to paddleball in order to increase velocity and control. Unlike most racquet sports, such as tennis and badminton, there is no net to hit the ball over, and, unlike squash, no tin (out of bounds area at the bottom of front wall) to hit the ball above. Also, the court's walls, floor, and ceiling are legal playing surfaces, with the exception of court-specific designated hinders being out-of-bounds. Racquetball is played between various players on a team who try to bounce the ball with the racquet onto the ground so it hits the wall, so that an opposing team’s player cannot bounce it back to the wall. The sport is very similar to 40×20 American handball, which is played in many countries. It is also very similar to the British sport Squash 57, which was called racketball before 2016 (see below for a comparison). History Joe Sobek is credited with inventing the sport of racquetball in the Greenwich, Connecticut, YMCA, though not with naming it. A professional tennis and American handball player, Sobek sought a fast-paced sport that was easy to learn and play. He designed the first strung paddle, devised a set of rules, based on those of squash, handball, and paddleball, and named his game paddle rackets. In February 1952, Sobek founded the National Paddle Rackets Association (NPRA), codified the rules, and had the rules printed as a booklet. The new sport was rapidly adopted and became popular through Sobek's continual promotion of it; he was aided by the existence of some 40,000 handball courts in the country's YMCAs and Jewish Community Centers, wherein racquetball could be played. In 1969, aided by Robert W. Kendler, the president-founder of the U.S. Handball Association (USHA), the International Racquetball Association (IRA) was founded using the name coined by Bob McInerney, a professional tennis player. That same year, the IRA assumed the national championship from the NPRA. In 1973, after a dispute with the IRA board of directors, Kendler formed a competing organization called the National Racquetball Club (NRC), which eventually became the dominant professional tour in the 1970s. For a period of time in the 1970s, the NRC and the IRA both offered competing "Amateur" and "Professional"