Dad taught us refinements in the proper usage of electric wall outlets. We already knew not to stick fingers or other foreign objects into them. But we didn’t know how to take real advantage of their design. Turns out that it’s easier to plug anything being used temporarily — a vacuum cleaner, say — into the top socket, then unplug it after use. The lower socket would be reserved for anything that was going to be plugged in all the time — a lamp, say. Test it for yourself! Every time I plug or unplug anything, I think of Dad and this lesson about the need for flexibility and stability.