Where I made a hole for an extension cord, I made a plate to cover it with. For the hole like yours, I took a little piece of cut off scrap, and just in from one side I drilled a hole a bit larger than the cord itself. Then I cut from the edge of the scrap in to the hole to make a slot. (I think I just used a hand saw for this small bit of cutting.)
The hole, big enough for the extension cord end, from inside the coop
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And the cover, screwed to the outside to cover the hole. I leave this cord in place through the summer, but if I wanted to remove it I would just pull those two screws out.
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I did something similar on my run to take an extension cord through hardware cloth in a corner. I did remove this cord last summer, but left it in place this summer. Particleboard wasn’t the best choice here, outside, but it was the scrap I had lying around that was the correct size! I could have made it more secure by overlapping & screwing to the framing on a 2nd side, but I thought this was good enough in my situation, and I was lazy and preferred to just drill the hole on the edge instead of drilling it farther in and cutting a slot.
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Edit: and I see others have suggested the same since I started typing this reply last night, but I delayed posting to get pictures!
Also, I agree with the poster who doesn’t like the idea of hardware cloth against an electrical cord. That was really the major impetus for the board with cutout in my run, more than security.