That's like asking when you paint a still life what brush do you use. I use whatever ruler I need to get the job done. A 6x24", a regular 12 inch school, a 4x12, when I use large widths of material a measuring tape and yard ruler. When I first started quiting I used the yard stick, school ruler and measuring tape.

I did not know what a shape cut ruler was either. I have never folded the fabric twice to cut strips. I cut the wof using my 6.5 x 24. How about the rest of you...do you fold your fabric twice and use a smaller length ruler?

8x24. used to have a 6x24 but sombody stole it at a quilt retreat!! Can you believe it, had my name on it and everything. Oh well. Now I have the 8x24 and I love it, took a while to get used to, but I like it een better.

I use 6" square most often.

Same here, except my square is 12 1/2. I use the June Tailor slotted thingy a LOT.

I fold, but I still use the same ruler.

In order of usage:
6x24
4x13
6 1/2 Square
12 1/2 Square up

My 6 x 24 the most

I don't because I am too much of a klutz! I use the 6x24 and work very hard to make sure I can get the one fold straight! Two folds is more than I can manage! LOL

Learned something new today. Thank you for mentioning watching a video to learn to use the June Tailor shape cut ruler. I learned so much watching the video. I will try the ruler again, now.