Good for gathering things together and securing them. They also form the basis of more complicated knot formations.
One of the simplest knots. It will stop a line from fraying. It can act as a stopper to prevent a line running through a hole or pulley. It also serves as part of a more complicated knot.
Tied in the same manner as an overhand, but after being passed around an object. When an overhand is tied back onto its own standing part it is said to be a half hitch. This is what distinguishes a half hitch from an overhand, and two half hitches from a clove (a clove hitch is when the line is tied around something else, not itself).
An overhand knot followed by the opposing overhand knot makes a square knot. It’s also called a reef knot because it was used to reef sail. Tying two overhand knots in the same direction makes a granny knot, which will loosen and may capsize and spill. This knot should never, ever be used as a bend and tied to join two lines under any circumstances, as it will fail.
Generally used for when a line needs to travel in a semi-secure fashion from one object to another (such as fence posts, or ratlines across shrouds in the old days). The clove hitch easily falls open if if shock loaded without the ends being secured in some fashion. This being said, when locked with an additional overhand, this is how crab pots all across the Bering Sea are secured, and so it can be used to great effect to tie two things together if tied correctly.
Shown here next to a single hitch for comparison. This is used to trice (tie) up packages, hammocks, sails, or any other object that requires some amount of gathering and securing. The difference between the single hitch, shown left, and the marline hitch, shown right, is that the marline hitch is the more secure of the two. If one were to imagine the package disappearing, in this instance, and the two respective knots drawn up, the marline hitch would form an overhand knot while the single hitch would capsize into an unknotted cord.