For Christmas, I gave Mom several presents, including a set of artisan felted wool coasters. The set consisted of two yellow coasters and two blue coasters, with an artsy silkscreened design on the top of each coaster.  

After a few months, I noticed that Mom consistently used the blue coasters on the correct side and the yellow coasters turned over to wrong side.

"You don’t like the yellow coasters?" I asked her one day.

"It’s fine."

"Then why do you turn it over to this side?"

"What’s the difference?"

I flipped the coaster over.  "This side is the design side."

"Either one.  No difference."

"There’s a difference:  This is the design side . . . this is not the design side."

"It’s you who buys it, not me."

"That’s true, but I intended for you to use the design side."