The words “lay” and “lie” may be the least favorite words of marketers who work for mattress firms or furniture stores. I don’t work in either of those, but I will go to exceedingly great lengths to find another word just so that I don’t have to endure the “lay” versus “lie” debate.
Sometimes the unavoidable term is “lay” or “lie.” I recognize the fact and respond accordingly; I go to the writing rules and reexamine when to use “lay” or “lie.”
The word “lay” means “put” or “place.” Its meaning necessitates a direct object. The word is, in that way, akin to the word “set.” One always “sets” a direct object, a particular thing, be it the table or a stack of books on said table. Similarly, a person would “lay” a tablecloth on the table or, if on a picnic, under a tree in the shade.