The Fifth Step

You can see the sunlight there on the wall and across the stairs leading upstairs. The glass in the front door throws unusual patterns.  We designed and built the house about thirty five years ago and that fifth step- you can see a bit of it mid left side of the image with just a finger of sunlight on it, has always squeaked! I tried to fix it many times,many ways- and always failed. It finally dawned on me, the noise it makes is so familiar now that it would disturb me if it didn't !