How are Equipment and Locations related?
A location is a place; a machine is a thing in it. Every machine belongs to exactly one location.
Locations is the register of rooms, floors, and areas — the physical map of a site, each with its own security level (see location-proof, above). Equipment is the register of machines, each one tagged with the location it actually sits in.
A QR code on the physical unit is the gateway into that machine's whole record — every inspection, reading, and document, from delivery through today — so anyone on site with a phone can scan it and see exactly what's owed and what's already proven.
Stickers (on both registers) is where you print the physical labels — QR codes sized for a nameplate or a door — once the register itself is populated.