Sliding Door Cleaning
Sliding panels, tracks, and rollers.
A sliding door is the one piece of glass on a building where cleaning has a mechanical payoff rather than a cosmetic one. The panels get done, but the track is the part that matters. Grit, salt and lost screws collect in the channel, the rollers grind through it, and the door gets heavier by degrees.
Nobody reports a heavy door. They just start pulling harder, and then someone puts a shoulder into it, and eventually the roller goes and the panel comes off the track in the middle of a trading day.
So the track and the rollers get cleaned out as part of the job, not as an extra. It is the least visible thing we do on a building and the one most likely to save you a repair, which is a strange combination to sell and the reason it usually goes undone.