On the drawing board: The right size tool for the job.

Often the tools of the artist are whatever happens to be handy.  When the circles on your plastic geometry template aren't big enough you have to search around for something else to use.  Roll of tape?..coffee cup?...too big.  Skin cream lid?...too small.  Finally I found the perfect size ring right there in my nightstand. I think some of you know what it is.