A square knot is a simple, reliable way to tie two ropes together, created by looping the ends around each other in a specific pattern: right over left, then left over right. When tied correctly, a square knot lies flat and holds firmly under tension, making it one of the most useful knots for joining two pieces of rope of similar thickness.

Sailors have used square knots for centuries to reef sails (tie down sections of sail in heavy wind), and the knot appears in activities from camping to first aid. If you're tying a bandage, securing a bundle of sticks, or connecting two pieces of rope to make one longer line, the square knot does the job cleanly.

The name comes from how the finished knot looks: symmetrical and boxy, with the rope ends pointing in opposite directions. But here's the catch: a square knot can slip when the two rope ends are pulled in certain ways, so experienced rope users never trust it for critical tasks like climbing or rescue work. For those situations, you need a different knot entirely.

The opposite of a square knot is a granny knot, which looks similar but twists awkwardly (left over left, then right over left) and can slip or jam unexpectedly. Learning the difference matters: one is more reliable when you need it to be, the other isn't.