"사각 매듭" (square knot) is a type of knot commonly used in various applications, including sailing, camping, and first aid. It is formed by tying two overhand knots, one on top of the other, with two ends of rope or string. This knot is known for its simplicity and reliability, making it easy to untie after use. The square knot is often used to secure two pieces of rope together, especially when the ropes are of similar thickness. It is important to ensure that the knot is tied correctly to prevent slipping. This knot is also referred to as the reef knot in some contexts.