I also say " 15 by 1" . With wood, you have a two by four, written 2x4, and no one would think of calling it anything but a "two by four"
though I have no idea if the numbers for the needle mean anything - while those for wood are actual dimensions. (Rough cut, before it's planed down to 3.5" by 1.5"). In this old house we do have some walls that were made with rough cut boards - real fun trying to patch in a few studs where an opening had been.