How do Mail Clerks keep track of packages in transit?

Mail Clerks primarily use tracking numbers and online systems to keep track of packages in transit. This method is efficient and allows for accurate monitoring of every package's location as it moves through the delivery system. Each package is assigned a unique tracking number that can be scanned or entered into online tracking tools, enabling clerks to access real-time information regarding the package's status, delivery route, and estimated arrival time. This system also allows for better communication with customers, as they can track their own packages using the same tracking numbers.

The use of tracking numbers and online systems streamlines the delivery process, reduces the chances of lost packages, and enhances overall operational efficiency. The other methods referenced, such as relying solely on barcode scanners, memorizing contents, or visually checking packages on a strict schedule, would not provide the same level of accuracy or efficiency in tracking and managing packages in transit. These alternatives might be parts of a broader process but do not encompass the comprehensive tracking system that uses tracking numbers and online tools effectively.