I think the one I have is 1/4" width. The material goes into the tool, the tool folds over the "seam" allowance as you pull the tool across your strip of fabric...it's totally easy!
I believe there are directions but if you want 1/4" I think I cut the strips into 3/4" width. That gives you the two 1/4" seams and the 1/4" bias strip.
To start it I cut the end on an angle - for me it was easier to slip the material into the tool. Like I said before Spray Starch the strip and let it dry THEN iron it. (letting it dry before ironing will stop the scortch on your iron) Slip the angled end into the tool - gently pull the fabric and let the sides of the curl over the strip of fabric... As you pull it out of the tool run your iron over it. You'll pull the tool over the strip as you run the iron behind the tool on the fabric. Make sure your strip of fabric is laying straight on the ironing board and when pulling the tool across pull it straight! Watch your seam allowances...if one side become less and the other side more...slide your tool BACK up and iron that section straight and try again.
(I think the bars are much would result in many more burned finger tips )
ON SALE!!! maybe I need to buy a couple more! HUGS and good luck!