2 trivial questions about vacuum cleaners and duvet covers

[Jumbuck]

Vacuum cleaners: somewhere along the hose there is always a small plastic sleeve which, when you slide it across, reveals a hole. Since this never seems to make any difference to the amount of suction, what is it for?

Duvet covers: why are these always done up with little poppers that come apart so easily, resulting in the duvet escaping out of the hole? Why not a zip to keep it closed properly?

[alzheimer]

Can't help you with the vacuum problems - but as for putting zips in duvet covers....sounds good until the zip snags/breaks or twists as they can do with repeated washings. At least you can replace poppers easily - and with bigger ones - if needs be!!

[ChuckFickens]

the hole in the vacuum cleaner pipe is to reduce suction so you can clean things like rugs without lifting them off the floor.

[Jumbuck]

Forgot about the washing aspect to duvet covers. I suppose that's as good a reason as any. (I posted this today because half of them had come undone overnight, yet again)

[Jumbuck]

I guess I'm just not observant enough to notice the change in suction with vacuum cleaners.

Thanks alzheimer and ChuckFickens.