OMRON P2RF-08-E relay socket mounting question

[ckambiselis]

I ordered a few of these relay sockets for a machine I'm building and haven't seen the M3 mounting holes, these have in the middle, on other DIN stuff I have used before, can someone elaborate on how the mounting hole is used, nothing really comes in mind on how it would work on a DIN rail that is mounted in place and couldn't find anything on a quick search. Unless the idea is to use a bolt and nut while the rail is not in place?