Can you say Neodymium? (nee-o-dim-ee-əm) It's what makes modern-day magnets strong enough to grip through one or more layers of fabric.
A thin piece of sheet metal mounted within the structure allows dimensional letters (with magnets attached) to be placed anywhere on the structure, with no visible means of support.
Magnets are mounted to both the frame structure inside the fabric, and to the back of the YES sign and the Intel logo. Magnet-to-magnet mounting gives precise alignment, while magnet-to-steel allows adjustment.