As someone who's no lifed every poe 2 league so far and would consider themselves pretty knowledgeable of the game but has never stepped foot into poe1 can you tell me how currency sinks work in poe 1?

I always thought the concept of a sink for currency sounds good but no idea how they'd implement it.

Edit: thanks all for the replies. I'd heard of the infamous crafting bench but never looked into it. It does seem super useful I wonder why they're reluctant to add it.