The holes for connecting the garage floor to the wall between the garage and the house.
You can also see a couple of the holes for similarly connecting the landing at the top of the stairs. We found the 6" hole saw in McMaster Carr's online store. Unlike Grainger, they're willing to sell to private individuals like us. I marked the height with the laser level, started the holes with the hole saw, and finished them with General Tools' Quad Saw/Driver coupled to a 10" long sawzall blade.