Hi -
The fabric folding pen is tube-like pen into which you put in 3-5 drops of a provided liquid (mild starch) and then fill the tube with tap water. (About 6 inches long) To use it, you run the "sort of" foam point of the pen along the seam stitches. (May have to squeeze the tube to get the water solution going the first time). It wets the stitched area. You then fold the fabric back , "pressing" the seam to one side. You do not have to press hard - start in the middle and gently slide your fingers to the edges - no stretching occurs as long as you don't pull hard on the fabric. Hope this explanation helps. OH - when the liquid is gone (lasts a LONG time), you can use drops of "Best Press" instead. Made by Clover. You can search the web for "Fabric Folding Pen" and get a bunch of sites.