So you buy a nice two shelf bookcase but it’s wobbly and you know it won’t hold much. I’ve recently gotten one and my solution was to put L-brackets on it. After installing about 8 of these brackets at the cojoining parts of the shelving, it is now completely stable and ready for use.
I don’t use diatomaceous earth as I don’t want to harm helpful things like spiders.
The things I’ve used to deal with ants that refuse to stay outside are cornmeal and Borax. They take both back to the nest. They eat the cornmeal and it blocks their digestion. The borax is mixed into a thick sugar syrup and I put it outside in a bottle cap. It will poison the ants but not your pet in the amount used.
The hardware store used to carry a tea tree oil spray (Hot Shot Natural) which actually worked very well, and I have a poison spray (Ortho Home Defense) that is supposed to be animal safe after it dries. Those both work on stuff which just refuse to be dealt with by the food remedies.