Stratagene developed a method called seamless cloning using Eam1104I and PCR described by Padgett and Soge in Gene 168 (1996) pp31-35. NEB doesn't have a license for either of these techniques. The technique uses a primer containing the side of the asymmetric site that contains cytosine. PCR is performed using methyl cytosine. All internal sites are blocked leaving only the primer generated sites as cleavable by Eam1104I or an isoschizomer with similar methylation sensitivity.