I save cleaned eggshells and when I have a pile, I pulverize them in my blender, then allow to dry fully. I collect in a zip-type plastic bag until I have several cups.
I then sprinkle a border of this around the base of our house to keep beetles and slugs and other critters at bay. It works very much like diatomaceous earth controls these kinds of pests.
I have been doing this for years—even as a lowly renter in my single days, and never had a problem with intruders. I must say it doesn’t work on spiders, who don’t bother me as they eat bugs.
The added benefit of eggshells instead of diatomaceous earth is that the rain doesn’t wash them away or render the effect useless, as happens when diatomaceous earth gets wet.
I love this idea as I had to move to a place that does not allow compost piles. It’s satisfying when I find info that allows me to keep something out of the landfill. It’s a double win, thanks!