What use was a glue that peeled right off?

In 1968, Spencer Silver, a chemist at the company 3M, tried to make strong glue. He got the opposite: one that stuck lightly and peeled off.

For years, nobody found a use for it. Then coworker Art Fry kept losing bookmarks from his choir songbook.

Fry coated them with the weak glue. They stayed put and peeled off cleanly. Sticky, peel-off paper works for notes too: 3M later sold it as Post-it Notes.