I have one of these and yes they work. Just sew a little inside the lune.

I have one and have used it many times over the years. A must have quilting tool.

Annie

I have 3 different sizes and use them a lot. They are very handy.

I have one and don't use it. Takes to much time to draw three lines when I can use my 1/4" foot and draw one line..

Just got a 12-1/2 inch ruler to help in HST. Since I need a "scant" 1/4" seam on either side of the bias line, my ruler was just what I needed. My eye-balling method had too many variances.

Two in a package by Fons and Porter.
I use them alot since I cant seem to sew a straight line.
For scant just sew inside the line a little.
You draw 2 lines, kinda tricky since the ruler is only half an inch wide.

I have 3 or 4 that I never use.
For me, it's much easier to pencil draw a diagonal line and sew on either side 1/4" away from it.

Buy the one that has a slot in the middle and edges that are 1/4" on either side. I use it for 1/2" sq triangles. You put point on each corner diaginally and draw lines on both edges and then sew on these lines and cut down center. This gives you 1/2 sq triangles. It is not really very time consuming to draw 2 lines (not three) and makes triangles easy. Actually this ruler is not very expensive and is well worth the cost even if it not used often. Anything to make you life easier.

That is what I usually do. Sometimes I think I just want a new gadget and sometimes I actually love that I bought it and other times I could smack myself upside the head...

Not sure which category this would fall into. lol

THIS is the one I was talking about. No sense in drawing 3 lines unless your cutting is off as well.