Because I asked him to provide a video of how to clean vents without water entering the property through the vent or causing runs on the glass.
The vent looks lovely and sparkly whilst you're cleaning it, this doesnt eliminate the fact that water will find its way through the vent into the property and also whatever sprays up into the vent will run back out afterwards bringing with it all the debris that collects in those things. Onto the glass.
Thanks for the video.
Ive also done that myself on older vents, and knocked half the buggers off. Which also seems to make it pointless.
You may be right, I wouldnt like to trust vents on my work to be honest, Ive had run-backs and flooded bedroom cills. It happens. You cant argue with gravity.