Here's an object you'd never guess the function of just by looking at it:
Designed for households with hard water, this Limey doodad is used to descale faucet heads. You fill it halfway with descaler or vinegar, hang it from the tap with the head submerged, and let it sit for 10 minutes. Then you remove it and run the tap.
The hole is so you can hang it from the base of the sink between uses, or the neck of your bottle of descaler, so you don't misplace it.
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