Decals come standard with adhesive and this is designed to stick
to your surface. Different quality decals have different quality
adhesives. Some are designed to be long lasting, others are
repositionable and other for high traffic areas like laptops.
The 3M vinyl decals are made with mini dots of glue and once you
are happy with your positioning, you push the front of the decal
and this pops the mini dots of glue and forms a strong bond with
the surface, very clever.