The runestone U 115 consists of five fragments, which were (re)discovered at the beginning of the 1950s in the foundation of a building at the farm Nedra Runby in Ed parish, north of Stockholm. It has been assumed that there is no direct fit between the fragments, but a closer examination shows that they make up an almost complete runestone with only a few runes missing. This conclusion is substantiated by some previously overlooked accounts from the 18th century, which makes it possible to reconstruct the whole inscription. The formulation of the text turns out to be rather unexpected, and the inscription does not seem to have been completed. In the article there is also a discussion of possible relations between the persons mentioned on U 115 and the family behind the runic boulder U 114 at Runby, as well as possible connections with the medieval noble family known as Rumby-ätten. Finally, the original position of U 115 and the relations to the other runic monuments at Runby are investigated.