This trophy, colloquially known as Log o'Wood, is the older and most important trophy in New Zealand domestic rugby.
It is based on a challenge system: the holding union must defend the shield in challenge matches and a successful challenger becomes the new holder.
In 1901 the Governor of New Zealand, the Earl of Ranfurly, announced that he would present a cup to the NZRFU to be used as the prize in a new competition.
When the trophy, a shield, arrived the NZRFU decided that it would be awarded to the union with the best record in 1902 and thenceforth be the subject of a challenge system.
Auckland, unbeaten in 1902, were presented with the shield.
In 1903 Auckland was in tour and did not play any home games, and thus did not have to defend the shield. The first defence was played in 1904.
The holder at the end of each season is required to accept at least 7 challenges.
Since the introduction of the National Provincial Championship in 1976, every home games a holder plays in the championship are automatically challenge matches, but not during knock out playoffs.
Since the split of domestic competitions in 2006, the remaining games to reach the 7 challenges are to be played against union from the other domestic competition.
If a challenger successfully takes the Shield, all of its home matches for the rest of the season are defences of it.