The bowline (/ˈboʊlɪn/ or /ˈboʊlaɪn/) is an ancient and simple knot used to form a fixed loop at the end of a rope. It has the virtues of being both easy to tie and untie; most notably, it is easy to untie after being subjected to a load. The bowline is sometimes referred as King of the knots because of its importance. It is one of the four basic maritime knots (the other three are figure-eight knot, reef knot and clove hitch).The structure of the bowline is identical to that of the sheet bend, except the bowline forms a loop in one rope and the sheet bend joins two ropes. Along with the sheet bend and the clove hitch, the bowline is often considered one of the most essential knots.Although generally considered a reliable knot, its main deficiencies are a tendency to work loose when not under load, to slip when pulled sideways and the bight portion of the knot to capsize in certain circumstances.[citation needed] To address these shortcomings, a number of more secure variations of the bowline have been developed for use in safety-critical applications.