Engineering
Engineering is one of the primary WoW Tradeskills. Engineering produces items that can be of value to any class, although they often require a specific engineering skill to be able to use the item. This skill was once considered very important to a PvP focused character. The effects of some of the devices has been toned down in recent patches in such a way that it is not an absolute requirement to have for PvP.
Classic
Engineering Schematics in Classic WoW
The Burning Crusade
A player can become a Master Engineer and begin creating items with schematics from the Burning Crusades expansion at Level 50, with an engineering skill of 275. Engineer trainers are found in Hellfire Peninsula at Honor Hold (Alliance) and Thrallmar (Horde), in Zangarmarsh at Telredor (Alliance) and Jabra'jin, in Netherstorm at Area 52, and in Shattrath City at Scryer's and Aldor's Tiers . Master Engineers can learn patterns up to 375 skill.
Wrath of the Lich King
A player can become a Grand Master Engineer and begin creating items with schematics from the Wrath of the Lich King expansion at Level 65, with an engineering skill of 350. Engineer trainers are found in the Borean Tundra at Valiance Keep (Alliance) and Warsong Hold (Horde), in Howling Fjord at Valgarde (Alliance) and Vengeance Landing (Horde), in Dalaran at the Magus Commerce Exchange, and in Icecrown at the Argent Tournament. Grand Master Engineers can learn patterns up to 450 skill.