Not sometimes.

Reliably, on the transition strip between the maths corridor and the main hall, where the tile changes and there is a lip of about three-eighths of an inch.

He knew the frame squeaked, and he knew the exact pitch of it, and he could tell from two corridors away whether she was coming.

He knew the seat upholstery had split along the front edge and that she had put a folded towel over it in the September and that the towel was navy blue and belonged to her mother.

He knew she had missed lunch twice in the preceding fortnight.