I put some on my long cutting ruler. 3-4 circles along each side; then more staggered in the middle.
They grip well, but there is a thickness to the grips, which raises the ruler off the surface; and that allows the fabric to shift in between the grips, so it doesn’t stay lined up completely with the mark on the ruler. Yes, you can nudge the fabric back to the line, but it won’t stay there bc there is no contact by the ruler there.
I hv had much better success with some grippy wrap I bought at Quilt in a Day. They don’t currently have this exact item in stock. Not trying to send customers away, but maybe a google search will find it. It’s called InvisiGRIP (#3057); it’s 1” wide. I just checked and MSQC has a form of it, but the size they carry is 12 1/2” x 1 yard, and that product seems to have adhesive on it, as there is a paper backing that needs to be removed. The style I bought is an inch wide and it’s sticks to the ruler by static cling, so you can easily reposition or remove it. You can also wrap spools of thread w it to keep from unwinding. It comes on a role. I use it for longarm quilting rulers, too. It’s thin, inexpensive, and you get a lot, so you can put a strip down the entire length of your ruler, or even several strips on a wider ruler. It’s also crystal clear. It cost abt $8 (two and a half years ago, when I bought it).