When shingle or clapboard siding has weathered severely, and is to be covered with new
siding the space below the the shingles or clapboards has to be filled with feathering
strips.


Feathering strips - Tapered wood filler strips placed along the butt edges of old wood shingles
to create a level surface when re-roofing over existing wood shingle roofs. Also called "horsefeathers."

Not just a Groucho Marx movie.