There are many instances where QR codes might be printed, or attached to an item in the field.
Under a user's profile you have the ability to download a QR code. Using your phone's camera, scanning a QR code will take you directly to that specific worker's profile. This is the simplest way to access a worker's competencies or certificates, while on the worksite.
One use case for this is to provide a quick way to see if a worker has the required competencies prior to starting a task. For example, is that user competent in running a specific piece of equipment? Are the competent in completing that required documentation? Are they competent in loading that trailer? You get the gist.
Another scenario might be when a user is required to produce proof of a certification. Scanning their QR code gives you quick access to items like their: first-aid certificate, proof of licence, TDG documentation, etc.
QR codes are meant to be printed, so don't hesitate to use them on id cards, stickers, crew sheets, etc.