To mount a 19" (or 10") PDU sideways in a wooden rack to save some space and not waste front panel space. I used it for a Digitus 19" 10xC14 PDU (https://www.reichelt.de/19-steckdosenleiste-1he-10-fach-digitus-dn-95404-p370749.html), but it should also work with any rack unit (19" and 10")that is not deeper than this one.