(with thanks to Matthew for his contribution)
The "paddle" received its name from its resemblance to the common boating accessory. A spanking paddle is usually made of wood, and has a broad face with a narrow handle (sometimes called the "neck"). Paddles are most popular in the U.S.A. When used as a spanking implement, the wooden paddle can be very painful. Because of its bluntness, the paddle is unable to cause stripes or wounds, like straps and canes can, but paddles can cause serious bruising when used excessively. While some paddles are designed to be small for "over the knee" spanking, most are too large for use over the knee. The common position for a paddling is the recipient being bent over while standing. While it is popular to have the recipient grap his/her ankles, this may be a difficult position to maintain since the force of the paddle, especially thick paddles, can knock the recipient off balance. Therefore it is often necessary for the recipient to bend over a sturdy piece of furniture such as a bed. Paddles can also quickly cause numbness in the recipient's buttocks, therefore it is advisable to allow plenty of time between swats in order to reduce numbness. Sometimes lexan is used as a substitute for wood, since lexan is more durable. It can also cause a greater sting with less bruising.
Some leather implements are described as "leather paddles" even though it is more accurate to call them a cross between a paddle and a strap. They have the unique effect of combining the impact of both implements, giving a greater 'thud' than a strap and at the same time increasing surface sting over a wooden paddle. They are preferred by some because of the sensation of leather against the skin, which of course requires their use on a fully bared bottom.
In the 1930's, American schoolteacher Harold Spencer developed the "Spencer paddle" by drilling holes in a wooden paddle. He created this holed paddle in order to reduce the cushioning effect of air by allowing the air to pass through the holes. Despite its appearance, holed paddles really don't make any significant difference in increasing the force of the paddle. Not only can air pass through these holes, but skin can as well, especially when used on the bare buttocks. This can cause blistering. The blistering effect can be greatly reduced by beveling the holes, since this allows more air to escape. Most paddles do not have holes drilled in them because of their ineffectiveness and tendency to cause blistering.
The paddle is the most common spanking implement in American schools that allow corporal punishment. The standard punishment given to students is three swats with the paddle. Because of the large amount of pain caused by the paddle, students are usually paddled while fully clothed in whatever they are wearing at the time of punishment. In some private schools that are single-gender schools, the student may be paddled over underwear or bare-bottomed. Because paddles can cause a great amount of pain when used over clothing, bare-bottomed paddling is often considered to be too cruel for use on students.
Paddling is often used as a rite of initiation is American college fraternities and sororities. These paddlings are often given over underwear or bare-bottomed. Since these paddlings are usually an ordeal that the pledge must endure only once, they are usually much more severe than paddlings given for punishment in homes and schools. Many times, the pledge will be given the paddle used on him/her as a souvenir. Paddles are often displayed in fraternity and sorority houses as a symbol of authority, even when they aren't used for discipline or initiation. Since these initiation paddlings are often considered to be very cruel, even bordering on torture, many colleges have banned this practice in "anti-hazing" measures. Even though many fraternities and sororities have banned paddling in their own constitutions, that does not stop this practice from occuring in secret.