Knuckle-Buster

A "Knuckle-Buster," colloquially known as a Zip Zap machine, is an old-fashioned manual credit card processing device. Its operation does not rely on electricity or electronic connectivity, which made it a popular choice in situations where modern POS (Point of Sale) systems were impractical. The device earned its nickname "Knuckle-Buster" due to the physical effort required to operate it, often resulting in bruised knuckles.

The operation of a Knuckle-Buster involves placing the credit card onto a flat surface of the device, over a slip of carbon paper that has multiple layers. The merchant then slides a bar or roller across the device, which presses the card onto the carbon paper. This action creates an imprint of the embossed card details, such as the card number, cardholder's name, and expiry date, onto the paper below. This paper serves as a physical transaction record that the customer typically signs to authorize the transaction.

While these devices are rarely used today due to the advent of electronic payment systems that offer faster processing and enhanced security measures (such as encryption and fraud detection), Knuckle-Busters can still be found in use in remote areas without reliable internet access or as a backup method during power outages or system failures.

Their continued, albeit limited, use underscores the importance of having a fail-safe payment processing method in the event of technological failures, ensuring that businesses can continue to operate and process transactions under any circumstances.