MAPLEWOOD, Minn. (AP) _ It was in 1974 that 3M scientist Art Fry, sitting through a boring church sermon, concocted the idea of self-sticking, yellow notes that can be removed without a trace, for use in his choir hymn books.

But it took him four years to convince superiors at 3M that this idea would sell commercially. Two years later, in April 1980, Post-it notes premiered, and America has been stuck on them since.

''Initial enthusiasm for a piece of note paper with adhesive on the back wasn't overwhelming,'' Fry said of his battle to persuade superiors. ''It was hard to sell the concept that people needed a note pad that would sell at a premium price compared to ordinary scratch paper.''

Now, a decade after the product hit the market, many Americans wonder how they got along without the yellow squares they stick to reports, folders, desks, computers, telephones and refrigerators.

3M started with two sizes of Post-it notes: 3 inches by 5 inches and 1 1/2 by 2, available only in yellow. Today, the company says it has more than 350 varieties, a range of different sizes and colors, plus many with cartoon characters and messages. There are Post-it notes specifically made for taking phone messages, marking book pages and identifying material to be faxed.

Company officials won't release sales figures, but say Post-it notes are one of the nation's top-selling office products, along with tape, copy paper and file folders. They're also big sellers in Japan - where the shape of the notes is long and narrow to accommodate the vertical writing of Japanese characters - and in Europe and most other developed countries.

''I had a lot of confidence that it would be a lot bigger than everyone predicted, but not this big,'' Fry said.

Fry, 58, was born in Owatonna, Minn., grew up in Iowa and attended the University of Minnesota, where he earned a chemical engineering degree. He started working at 3M 35 years ago as a junior at the university.

Now the equivalent of a division vice president, Fry still works out of the same small, corner office he moved into shortly after he devised Post-it notes. His desk is full of messages written on them.

For Fry, the idea of sticky paper was a solution to an annoyance that seemed to occur every Sunday at North Presbyterian Church in North St. Paul.

''I don't know if it was a dull sermon or divine inspiration, but my mind began to wander and suddenly I thought of an adhesive that had been discovered years earlier by another 3M scientist,'' he said.

In an attempt to produce a strong glue, that scientist, Spencer Silver, accidentally made an adhesive strong enough to hold paper but easily removable. No one found a use for the glue until Fry had his impulse.

Fry began developing Post-it notes the day after that fateful church Sunday. About a week later, he started finding other uses for his invention.

''I was writing a report that had a question that I needed to ask my boss,'' Fry said. ''So, I cut out a bigger piece of the bookmark sample and wrote the question on it and stuck it onto the report I was sending to him, and he jotted his answer down and stuck it on something that he was sending back to me.

''We got all excited because we knew what we had here was more than just a bookmark. It was a whole systems approach to communications.''

When Fry's superiors finally were persuaded to pursue the project, the notes didn't sell well. But Fry believed that was a case of people not knowing what they needed.

''I knew that people who were using them just loved them,'' said Fry.

Fry's pushing paid off in Boise, Idaho, where 3M officials gave away Post- it notes. Nearly all the recipients said they would buy them if they were sold in stores, and 3M finally was convinced Fry was right.

Now, Fry enjoys hearing about how people have used his invention, from lawyers who use them on legal documents to doctors who use them on X-rays to newlyweds who stuck dozens on their car.

''It's like ice cream,'' he said. ''I haven't found anyone that doesn't like it.''