The driver will knock first and then request to unlock your door with their Amazon handheld scanner. (amazon.com)
Hardware providers, such as the makers of handheld scanners used in warehouses, can also help point you in the right direction. (entrepreneur.com)
Some systems also include components like handheld scanners for taking physical inventory, bar code readers, credit card processors and signature - capture pads, and will support electronic catalogues and ordering. (petbusiness.com)