DIN-rail 35 mm top-hat mounting (EN 50022)
<a href="//commons.wikimedia.org/wiki/User:Markus_Kuhn" title="User:Markus Kuhn">Markus Kuhn</a>
<span style="border:1px dotted #FC0;padding:0 4px"><a href="https://en.wikipedia.org/wiki/File:DIN-rail-dimensions.svg" class="extiw" title="en:File:DIN-rail-dimensions.svg">DIN-rail-dimensions.svg</a></span>