6x6 Quilter's Clapper The Quilter’s Clapper has been designed to flatten those larger areas.  It is used to press seams without burning. Used with steam from your iron, press the area with the Quilter’s Clapper and hold for just a few seconds, it will leave a nice, flattened seam. The top is rounded over and smooth with a wooden knob for easy pick up. The wood is unfinished to better absorb the steam.