some one told me to use an index card to get the exact 1/4". to do this, do i put my 1/4" foot on one of the lines or do i but it up like i am using my fabric. i am trying to get my scant 1/4 from there. but i put my 1/4" foot on the line and then move my needle one movement. and when i look at my fabric it looks like a small seam. am i doing this right or am i just seeing it wrong?