The manual credit card machine that is called a knuckle-buster was named by the store clerks who use this device often. This portable and manual credit card machine operates as a slide bar is pushed over a carbon paper receipt that allows for a copy of the raised credit card numbers to be copied onto the receipt. The manual back-and-forth pushing on the knuckle-buster credit card machine can result in calluses to form on the knuckles of the store clerks who use this machine multiple times each day. Some credit card companies call their portable credit card processing machines a zip-zap card processor.
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