Have a wooden wedge cut at a lumber store to measure 7 inches long and 3 inches wide, and 2 inches high at its highest end.
Drill a hole through the thick end using a 3/8 inch or 1/2 inch drill bit. Sand with fine grain sandpaper.
Stain or whitewash;don't use paint, which will chip. Cut a piece of grosgrain ribbon long enough to go through the hole and over the knob, and tie.
Now I would never have thought of this one !!