Video: Knots may seem like an old-fashioned skill to learn, but they can actually be really helpful in a lot of situations. This video will teach you how to tie the constrictor knot, which is essentially the primitive version of the zip tie.
This quick lesson from the ITS Tactical YouTube channel explains how to tie the hard-binding constrictor knot. You can use this knot to close and secure bags, tie something to a pole or branch, bundle objects (like sticks, poles, etc.) together, and it's even used as a ligature in surgery. The knot has a very strong bite (it tightens down hard) and is very difficult to untie, but just like a zip tie, it's also very secure. The harder your rope or string gets pulled, the tighter the knot gets. Plus, it's easy to learn and you can tie it in a matter of seconds. If you want to untie your knot anytime soon, however, you're better off using the slipped variation (also demonstrated in the video).