Most of the time, sew-on patches are harder to apply, as not everyone has access to a sewing machine. Therefore it's best to iron on a patch as opposed to sewing. To iron on a patch, you will need to place your iron on a high heat and iron. However, don't press on for an extended period as your clothing may become melted or damaged. Plus, you can't use fabrics like nylon or leather to iron on patches.