Patches come with iron-on backing; applying heat directly to the patch face is not recommended. When applying, it is recommended that an iron be used for the appropriate heat setting of the material you are applying the patch to, and that the iron be placed on the inside of the material, so that the patch is face-down on a flat surface and the iron's heat diffuses through the base fabric into the adhesive, instead of through the patch's design. These recommendations are meant to help avoid the possibility of melting the polyester thread of the patch. For the most durable bond, you may want to sew the patch to the surface in addition to - or in lieu of - using the heat-based adhesive.
