Matrix door

A matrix door was a method of physically entering the Matrix on Gallifrey, as oppossed to merely connecting one's mind to the Matrix. (TV: The Deadly Assassin)

A number of these doors existed, with particular ones including the legendary Seventh Door outside the courtroom on Space Station Zenobia through which the Sixth Doctor, Mel, and Sabalom Glitz pursued the Valeyard, (TV: The Ultimate Foe) and the Eighth Door onboard the Time Station through which President Romana II came in contact with Rassilon. (AUDIO: Neverland)

The Valeyard hid another matrix door on the mudball planet orbiting Eta Rho, using it to escape the particle disseminator trap left for the Sixth Doctor and Inquisitor Darkel. (AUDIO: Trial of the Valeyard)