Online nshift documentation: Using Cloud Print for Shipment Server – nShift
Drop Zone is a program/service running on-premise which functions as an agent for printing freight labels and documents from nshift. Our purpose for using Drop Zone is to make sure the labels are printed at the correct location, e.g. where an order is picked and shipped from.
A common use-case is:

1. A new shipment is submitted using the nshift/consignor API.
2. Labels and documents are sent to the correct Drop Zone installation (on-premise, where we want to do the printing).
3. Drop Zone starts printing on one of the configured printers.