How is this pipe removed? Seems to have 2 points to be released


I am looking into how I can unclog my bathroom sink.
I am looking at the pipe underneath and it seems that it has 2 points that can be used to be released. Why is this? Does it matter which to use?
This is the v shaped pipe underneath the bathroom sink we usually remove when the sink is clogged.
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Best Answer

That looks like a double-ended compression coupling. It is used because most people cannot spin their sinks or houses around to unscrew them.

Use a pipe wrench to unscrew both ends of that coupling to gain better access to the pipe.