Figure-eight on a bight is a secure and versatile knot used for mooring a boat to a dock or mooring ball. It creates a loop that can be easily passed over a cleat or piling and tightened by pulling on the two ends. This knot is commonly used in boating due to its strength, ease of untying, and ability to hold fast under load. It provides a non-slip, secure connection that can withstand sudden jerks or changes in tension. The figure-eight on a bight knot is an essential technique for boaters as it ensures the vessel remains securely moored in various mooring situations.