Line locks should be fairly simple to use, they just slid up and down to tighten and loosen the guy line, and should be tied so they automatically grip the line and hold it in the position that you move it too. As people have said, this makes it much easier and quicker when you’re wearing gloves or you’re fingers are cold and a bit stiff and numb. Also makes it a bit quicker if you need to jump out in the middle of the night and quickly adjust, rather than having to untie and retie knots etc.
The most common ones are usually the little triangle shaped ones as shown in this video (these are big chunky ones, on a backpacking tent its normally the same design but a good bit smaller)….
I’ve got small versions of those little triangle ones with 2mm dyneema cord for my guys and they work great.
The ones you seem to have, linked to in the other video a few posts above are a different design, I hadn’t seen them before, but also seem to work well, long as they grip the cord OK then should be much quicker to adjust than knots.
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