The standard means to register a device for Windows Autopilot is for the hardware OEM to register the device during the device OEM factory provisioning process, as the device is built it is automatically registered via the Windows Autopilot deployment service. This process allows for devices to be assigned an Autopilot profile and configuration before they are shipped to the client users. Where this OEM registration process is not used the other option is to generate a hardware hash from the device and manually register the device on the clients tenant.
Microsoft have now provided another option to enable a device for Windows Autopilot. OEMs are starting to ship devices with a Product Key ID (PKID) label printed on the outside of the device box. This can be scanned allowing for the device to be registered for the client without the need to even open the box.
This all ties in very well with the new options Microsoft are providing with Windows Autopilot white glove, allowing for onsite technicians to configure devices locally in advance before the device is handed over to the user. This reducing user down time and improving the user experience.