user50022: They have holes for screw on, on top of the holes on the Arduino itself. Where can I find parts that are compatible with this case/cover? What was the intended use of this case/cover? Thanks.

user37622: The cover was developed for Arduinos with on-board Ethernet with POE and similar cover has the Ethernet shield with POE. POE - power over Ethernet is 48 V, so it is better to not to touch a soldering point with this voltage.
The arduino.org boards were sold with this cover. Some of them had on-board esp8266 and soldering points leading to esp8266 sensitive pins. Again, better not to touch.
I used the cover to attach the Arduino to a DIN rail over a DIN rail clip.

50022: <p><a href="https://i.stack.imgur.com/pJ4IM.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/pJ4IM.jpg" alt="enter image description here"></a>They have holes for screw on, on top of the holes on the Arduino itself. Where can I find parts that are compatible with this case/cover? What was the intended use of this case/cover? Thanks.</p>
 37622: <p>The cover was developed for Arduinos with on-board Ethernet with POE and similar cover has the Ethernet shield with POE. POE - power over Ethernet is 48 V, so it is better to not to touch a soldering point with this voltage.</p>

<p>The arduino.org boards were sold with this cover. Some of them had on-board esp8266 and soldering points leading to esp8266 sensitive pins. Again, better not to touch.</p>

<p>I used the cover to attach the Arduino to a DIN rail over a DIN rail clip.</p>
