....to protect the iron from goo.......for pressing cloth in insructions. This would be something you lay on top of fabric pieces that are ready to be fused to another piece of fab or to make a larger pieced of something to later be fused..and then lay down pressing cloth then iron on top of this. I use an old kitchen cloth towel, but that suggestion of parchment paper also sounds good. Some fusible appliqué also say "damp" pressing cloth for final fusing, which is why I use cloth kitchen towel but any piece of cotton muslin would do..