Hopefully this isn't old news. I use two caribeners and two pieces of static line.
First double your piece of line. Next tie a series of overhand knots along the doubled line.
Loop the line around a tree etc running one end through the other.
Next attach your caribiner through the correct loop to adjust tention.
Do the other side and enjoy. I have a couple of ideas to refine the system and even use webbing.
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