They're a guide for FMQ so you'd drop the feed dogs. You also need a ruler foot that's tall enough to prevent accidents.

You are correct, you do not use the IDT when FMQ. Quilt on.

I know you don't use the IDT, but when using a thicker ruler, the IDT, even though raised up, can get in the way; so that's my question regarding these particular rulers.
Thanks!

They are the standard 1/4 inch thick.

I have a Pfaff 2030, older machine. I do a lot with my walking foot, but would like to do more fancy designs. and would like to try the rulers I see advertised. What have you used and what would be the easiest to start with?

If you do a search on this forum under "Westalee Ruler Work" there is lots of information that will be of help to you. Here's just one:
https://www.quiltingboard.com/main-f...s-t291248.html

I have the "sqiggy" and "archie" rulers, which I am using with the Tiara. I did find I had to put extra gripper stuff on, I used the Handi Grip tape. On the sqiggy, I put the tape on both sides so I could flip it. The built in grippy spots on these weren't gripping enough for me to push the quilt around. But there is a lot you can do with the sqiggy curve, and the archie, so I think they are worth it.

When using one of my Pfaffs with IDT, to disengage the IDT, reach behind the presser foot and grab the extra foot back there and pull it down and slightly back, then let go. That should make the IDT foot retract up enough to be out of the way for what you propose to do.