The carrick bend is used to join very heavy rope or cable that is too large and stiff to be easily formed into other common bends. It will not jam even after carrying a significant load or being soaked with water.
The Rover Network Badge is a Carrick bend
The eight crossings within the carrick bend allow for many similar-looking knots to be made. The lines in a "full" or "true" carrick bend alternate between over and under at every crossing.
If the two ends emerge from the knot:on the same side it is called the double coin knot. The form with the ends emerging diagonally opposed is considered more secure.
Unfortunately, with so many permutations, the carrick bend is prone to being tied incorrectly.
The carrick bend, also called full carrick bend, sailor's knot, and anchor bend, is perhaps the nearest thing we have to a perfect bend. It is symmetrical, it is easy to tie, it does not slip easily in wet material, it is among the strongest of knots, it cannot jam and is readily untied. To offset this array of excellencies is the sole objection that it is somewhat bulky. Ashley Book of Knots
The carrick bend is generally tied in a flat interwoven form and will collapse into a different shape when tightened, a process known as capsizing. The capsized form is both secure and stable once tightened, although it is bulkier.
In the interest of making the carrick bend easier to untie, especially when tied in extremely large rope, the ends may be seized to prevent the knot from collapsing when load is applied. This practice also keeps the knot's profile flatter and can ease its passage over capstans or winches.
The ends are traditionally seized to their standing part using a round seizing or a series of double constrictor knots may also be used. When seizing the carrick bend, both ends must be secured to their standing parts or the bend will slip.
- Clifford W. Ashley, The Ashley Book of Knots (New York: Doubleday, 1944), 262–263.