My grandfather used to do a lot of gardening in his younger days. He also frequented garage sales on a weekly basis, accumulating lots and lots of junk. I came across a couple hundred of these little things and have no idea what they're used for. Knowing him, these might not have been used in his garden - in fact, they might have no use in a garden at all. They were kept in his backyard garden shed, but that's all I really know.

I have a garden myself and would use (some of) these parts if I knew how and for what purpose.

When assembled with a piece of hose connected, they look like this:

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The gray cap comes off and each end looks like this:

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