I use the one called " Quick Quarter Ruler" it is blue - like this http://www.quiltersrule.com/template/qr-qq.html

Or you can get these rulers at Nancy's Notions, both in the same package: http://www.nancysnotions.com/product...r+ruler+set.do

I have this one and love it!!

[QUOTE=cmrenno;5214297]Fons and Porter call their's Quarter Inch Seam Markers. There are two sizes in the package and I think that you can find them at Joann's. Here's a link http://www.joann.com/search/_quarter_in_seam_marker/

This is the ones I bought, got em at Hobby Lobby, same price. I love em! Nothing more to say, but the thing keeps telling me my message is too short! Happy Quilting Everyone! How ridiculous is this, still won't let me post!

The angler is very helpful in making half square triangle, it is a piece of plastic that clings to your machine and has lines marked on it and you guide you fabric using the angler and you don't have to mark the squares, it is a time saver. http://www.connectingthreads.com/too...gler-2-tool_TD... - Cached

I've used the Quick Quarter Ruler but now prefer the Omnigrid Ruler Trio.
The set includes a 12-inch, 6-inch and 4-inch ruler. This is where I got mine
but you probably can get it cheaper in the US.
https://www.agreatnotion.com/product...&productId=762

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Fon's and Porter is the tool you're thinking of. If you do not want to purchase one, just draw a line with a ruler thru the center and sew a quarter inch on either side of the drawn line. It works just as well. I was introduced to a pen called FriXion. one end is an eraser to rub out the lines, or It comes off with a Hot dry iron. It's made by Pentel.
It comes in three colors red blue and black. I suggest you give it a try. It costs less than the rulers.
AuntJudy14