Wednesday evening I came home to find yellow tape blocking the stairs. I tried a side door but found, in accord with past experience, that none of my keys work in it. As it was after hours I had no alternative but to stoop under the tape so I could get to my apartment, even though the new paint on the stairs was still sticky.
Yesterday a neighbor told me she has a key that lets her in the side door. She said she'd show me the trick when she sees me again, but I don't know when that will be as I'm not even sure where she lives.
Meanwhile another neighbor had pointed out that the usual procedure is to paint stairs one side at a time, so that residents don't have to look for alternate routes.