Blank stickers, or 'slap tags,' have been a part of graffiti culture for decades now. They may have been around as early as the '80s, but I didn't see them until the '90s. Blank slaps are a good way to get tags up quickly and in a less risky way than actual marker graffiti tags.
In the early days, they were all repurposed from other sources, like the paper Priority Mail labels, some UPS and FedEx labels, and the popular 'Hello My Name Is' blank name tag stickers. The white space on these stickers provides enough room for a tag or two, and the branding became part of the overall look.
Collectors began searching for older, discontinued versions of the USPS labels and even started selling them online. It is not uncommon to find artists still utilizing these repurposed labels for art and graffiti, but now we have companies and individuals creating their own designs of blank slaps.
It's interesting to see the evolution of graffiti slap tags, and it will be interesting to see where it goes in the future.