This places fixtures at between 3/4 and 7/8 of the height of the door and lets those approaching the door knock or gain entry without glare in their eyes. Lights need to be high enough to illuminate the immediate porch area and steps within a few feet of the door.
intermediate definition an intermediate is a substance formed during a middle step of a chemical reaction between reactants and the desired product examples in the chemical equation
In chemistry a reactive intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these compounds be isolated and stored, e.g. low temperatures, matrix isolation.