To which scale are you referring? The ruler that I use has ten equal measurements once you calibrate it with the arrow under options to make it so. Once you have it the size you want it and in place, just hit F5 to keep it on top of the window. The edges will be a darker black to show that it's on top, plus you'll know because it'll stay there.
The thing I like about my ruler is that not only are there ten measurements by number, but it has half, quarter, and even eighth of a unit marked. That way you can be a LOT more precise than guessing how far between each unit you need to go. Also, the line can be moved to keep track on that shot where you need to stop on the ruler.
Since the putter meter is different from the other clubs, I use two of my rulers and put the putter meter (Which always stays in exactly the same spot once I close and reopen it) on the bottom, right below the meter, and another one on top of the meter for full clubs. The only thing about that is that you have to open two rulers, select one of them, and drag it up. You'll also have to stretch it out a bit to fit the full club meter. Then go to options>calibrate and select inches, then back to centimeters (To get those extra black pixels off the ten end. Then arrow it over to make it ten equal units and hit OK.
While the second ruler is a bit of work, it takes about 1 minute to move it, resize it, and calibrate the second ruler once you're used to it. But it's ready for as long as you play that day until you close it down. The putter ruler, you never have to touch.
It's up to you guys which ruler you use. Personally, I'd rather have it exact down to the 8th of a unit rather than just whole units and guessing. Also, I don't mind the one minute of work per day and also having two rulers, one on top and one on bottom of the meter. But to each their own.