You can see just enough text to know you’re looking at a medieval German text, and what you can see doesn’t seem to be devotional. You can try to imagine the rest of the words, but you don’t have much to work with. If all you had were a few letters from a vertical column of words, you’d probably give up, but the ends of two lines are visible, so you know you’re dealing with verse. It might even be from one of the Middle High German classics. So you start checking. Does in kurtzen tagen ever rhyme with wurden derslagen in the Nibelungenlied? No, it does not. Somewhere in Hartmann von Aue, maybe, or Wolfram von Eschenbach? No and no. And then you discover that the corpus of Middle High German literature is much larger than you had ever thought, and your only option for figuring out what your fragment is appears to be reading all of it.
However, scholars in the nineteenth and twentieth centuries produced a great number of scholarly aids that are not often used today, including indices of rhymes for all the major and many minor authors. Rhyming indices are very helpful for trying to determine the dialect of the original version if it seems that the text rarely or never rhymes words that would rhyme in some dialects but not in others – and also for finding instances of poets who rhyme tagen with derslagen.
If you check enough rhyming indices in your library or ordered via interlibrary loan, you will eventually discover such a passage in Hugo von Trimberg’s Renner (thanks to Franz Diel’s 1926 Reimwörterbuch zum Renner des Hugo von Trimberg), and the following text will match up with the visible portion of the remaining lines. And there will be much rejoicing.
In the published article, the section on Der Renner was just a few pages, but that page took months of following up on dead ends before I found the text I was looking for. As for the fragment, it proved to derive either from the lost first volume of the Hausbuch of Michael de Leone, one of the most important fourteenth-century collections of German literature, or from a similar manuscript by the Hausbuch copyist.