Cleat

Cam Cleat

The cam cleat has two cams that allow the line to be pulled in one direction, but locks the line to hold it in the other. It is released by pulling the line up out of the cams.
Low Profile Sail Line Cleat

This is an aluminum jam cleat. The line is fed through a hole (on the opposite side from that shown in the photo) and jammed into the ridges shown to the right. It is released by pulling the line to the left.
Horn Cleat

The horns on this cleat can catch on clothing and gear. Not recommended for kayaking.

A fitting used to provide for a temporary attachment of a line.

There are several types of cleats.

Cam cleats use one or two cams to grab the line. The cams are eccentrically mounted, rotating bits between which a line is passed. If pulled in one direction, the cams open and the line runs free. If pulled in the other direction, the cams close and hold the line fast.

Jam cleats are cleats with a V shaped groove in it. The groove is lined with oriented ridges. When tension is put on the line in a direction against the ridges, the ridges force the line into the V and the line is held fast. If pulled the other way, the line releases. Jam cleats can have a vertical or horizontal V groove. For kayaks, the horizontal ones offer a lower profile. They are also available with a cover or in an enclosed design so that there are no "hooks" sticking up to catch on gear or clothing. The latter are desirable for safety reasons. Jam cleats are also called clam cleats, but that is a brand name.

Horn cleats have a "horn" sticking out either end. The line is wound once round the base and then over the "horns" in a figure-eight pattern to secure the line. They don't release quickly. The "horns" also catch on gear and clothing and represent a safety risk. Not recommended for kayaks.