I'm going to try to attach a couple of pix of my ceiling-mounted AP here. If this works...
In the first photo (which looks like it came out upside-down, sorry about that!), notice my issue with seeing the backside of the AP --- it's mounted too close to the ceiling beam behind it, so I can't get my head/eyes up there to see much. So I got more creative & I stuck my smartphone camera up in there to get the second photo. It's a bit blurry, but you can see the blue ethernet cable plugged into the back. Given the super-limited field-of-view I have through the cutout on the back of the AP cover, maybe you can image why I was attempting to remove the cover. I still don't see any way to release anything --- the smaller slot next to the larger cutout on the back of the cover is directly in front of a power port on the AP. If this AP ever dies, I have no idea how to get it off the ceiling to replace it....
< continued in next post... >
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