Chevron

A chevron is a V-shape, often used in architecture as a fret. All known Stargates have nine chevrons used to lock in coordinates, with the exception of the Asuran Stargate Satellite, which only had eight. The top chevron 'scans' each co-ordinate and the corresponding chevron lights up. Only seven of these chevrons are normally used, as use of the eighth, which allows transport to other galaxies, requires tremendous power (ZPM levels). The ninth chevron connects to a specific Stargate, as oppose to the normal method of connecting to a specific area and the gate inside it, and requires even more power still (the entire output of a planet's core). One such example of this is the Stargate on the Ancient ship, Destiny.

Stargate chevrons of the Milky Way galaxy glow a yellow-red color, Pegasus Stargates' chevrons glow blue, and the chevrons on Stargates similar to that on the Destiny glow white.

Tau'ri customs
At Stargate Command, a technician, usually Walter Harriman, shouts out the chevrons being encoded in the following manner: According to Harriman, he uses "locked" as a way to change things up.
 * "Chevron One, encoded."
 * "Chevron Two, encoded."
 * "Chevron Three, encoded."
 * "Chevron Four, encoded."
 * "Chevron Five, encoded."
 * "Chevron Six, encoded."
 * "Chevron Seven, locked."

On the Icarus base during the 9th Chevron dialling sequence, Technician Riley had a different approach:

As the gate was dialling a symbol for the address he would announce the Chevron was encoded, once the chevron locked in place, he would identify it as being locked in place.

In 1994, when dialing Abydos for the first time, a technician named Jenny shouted out the chevrons locking in a lengthier manner: "Chevron _ is holding," when the symbol came up on the screen and "Chevron _ is locked in place," when it locked.

In 2004, when the Atlantis Expedition arrived in Atlantis, the first thing Rodney McKay said when activating the gate was "Chevron One encoded", even though the Atlantis gate dials much faster than the dialling computer on Earth.

Behind the scenes
In Stargate Infinity, Stargates have eight chevrons.

In Stargate, the top chevron is different from the rest of the chevrons on the Stargate. Whether or not this has any effect on dialling, i.e. whether or not seven individual chevrons are dialled with the top being just to align the glyphs or if this top chevron serves as the seventh chevron - as in the series - remains unknown.