Lee Valley carry’s them, and I’ve seen them at commercial supply shops. I’ve never seen anyone use one, but I guess a VDE one would have some good applications over a measuring tape. I’ve also been using my laser measure a lot more lately, it eliminates a lot of the measurement errors common to measuring tapes.

if you mean the engineers ruler (6 1-foot sections in North America) then no, tape measure is more common. But the folding ruler is often seen in the trades where the measurements need to be more accurate than what a tape measure provides.

Measuring tape by a long shot. The only follding ruler I have, I got from Schweizer Electronics at an industry event. Many that do this for a living use laser measurement now too.

My (British immigrant) grandfather had a folding ruler, but that's the only one I have seen in person in Canada.

Measuring tapes are more widely used by a massive margin. Folding rulers are rare I would say. That being said I have about half a dozen, but all were provided by European manufacturers. I don't think I've ever seen one in a hardware store but I think you can get them on Amazon fairly readily.

That being said, maybe they are more popular than I think as I never need to buy one.

I have never heard of a folding ruler. I had to look it up to see what it is. I have never seen these in any stores. Tape is the default measurement device.