It takes fewer than ten hours to learn to type with ten fingers at around 15 words per minute and another five hours to learn to write at about 20 WPM. The most effective method is to study in a short amount of time. A lesson every day for ten days, followed by five days of practice typing, is advised. Also known as "finger typing", this method uses the index finger for the @ character, the middle finger for the # character, and so on. Although using all ten digits is beneficial for accuracy, some experts recommend only using each finger twice per week to avoid injury. Ten-fingered writers create their own problems. Because they have more finger movements to make per word, they can write less words per hour. In fact, it takes them about five hours to write what other people can do in three hours. They must spend more time thinking about what they are going to write and thus may not write as much as others who just start typing and may not stop until they have written everything that comes into their heads. In addition to being easier to do wrong, ten-fingered writing is also harder to do right. Because there are so many possible combinations, mistakes will occur more often than not, which makes editing difficult. Also, because certain letters require more precision than others, trying to write with enough accuracy to distinguish between words will be difficult. Finally, writing too fast will result in errors due to muscle memory.