Patches — facsimile

a manuscript page with a patch that is real, but has been separated, and is
              simulated in place

same page, no patch

This is from the MHS Jefferson project

You may encounter patches, or overlaid fragments of manuscripts, as you encode your document. These can function both as additions to manuscripts, or as a larger version of subst element. The TEI allows you to encode patches both ways, or to be completely agnostic about how the patch functions. In this example, we have two versions of the facsimile page: one that has the patch in the place that it was overlaid, and one that shows the original page without the patch.

Advanced Manuscript Encoding, slide 15 of 23