Years ago I asked my doctor friends how many holes are there in a human body? Answer: one (from mouth to ****). Everything else - lungs, genitals, bladder, etc. is an invagination. There are passageways, e.g. nostrils, tear ducts, Eustachian tube. But only one hole. We are coelomates.
Does that mean we aren't digging a post hole when installing a fence? Do I own a post hole digger or a post hole invaginator?