but what forces the previous knot to move out of the way (in this case move to the right) instead of having the needle jam in the same knot again and again? I still don't understand how it work without any kind of lateral movement, just a vertical one.
You basically attach a lot of weight, forcing the stitch to tighten, essentially pulling down the previous stitch and also priming the next stitch by having the current loop pass the latch
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