A square knot is a type of binding knot used to securely join two lengths of rope or string. It is formed by tying two overhand knots, one with the right end over the left and the other with the left end over the right. This knot is commonly used in various applications, including sailing, camping, and first aid. The square knot is also known as a reef knot and is valued for its simplicity and ease of untying. However, it is important to note that it is not suitable for all situations, particularly where the ropes may be under heavy load or if they are of different thicknesses.