Time lock

A time lock, or temporal lock, was a mechanism whereby an event or series of events was rendered unreachable by time travel, blocking off a section of the Time Vortex. The effect was described as being like a wall, (AUDIO: 1963: Fanfare for the Common Men) and Ace explained that a time lock could seal a planet inside a spacetime envelope, wiping it out of history. (AUDIO: Random Ghosts)

It was thought impossible to pass through a time lock, but this was proven false; Dalek Caan did so, but, in the process, (TV: The Stolen Earth) saw the whole of Time and Space and turned against the Dalek Empire, (TV: Journey's End) with his shift in behaviour leading Davros to the conclusion that the journey had "cost him his mind". (TV: The Stolen Earth)

There were also other workarounds to enter a location blocked by a time lock, such as the use of a stasis cube to displace and freeze a moment of time outside of the natural progression of reality. With the event in question suspended from the actual flow of time, one could then enter it directly without needing to physically travel through the Time Vortex. (TV: The Day of the Doctor)

Another method of bypassing a time lock was to follow one's younger self through to a time locked time and place, through a very precise window. The older traveller would be recognised as their younger self, and allowed to pass through. A time traveller had only one opportunity to try this. (AUDIO: The Shoreditch Intervention)

Most notably, the histories of both Gallifrey and Skaro were time locked during the Last Great Time War, (AUDIO: Legion of the Lost, The Shoreditch Intervention) as well as that of Earth. (AUDIO: The Shoreditch Intervention) The war itself would be time locked following its conclusion. (TV: The Stolen Earth, The End of Time)

Places unfortunate enough to be partially caught in a time lock could be splintered between timelines, as was the fate of Lujhimene when it was caught on the edge of the time lock used to seal off the Last Great Time War. (COMIC: Running to Stay Still)

The Sixth Doctor used his TARDIS to put a time lock on the TITAN Array by boosting its reality quotient above 1. (PROSE: The Quantum Archangel)

TARDIS component
The Doctor's TARDIS possessed a time lock. (GAME: TARDIS) When the TARDIS was suspended in space by the Great Intelligence, the Second Doctor wondered if the time lock had slipped, (TV: The Web of Fear) since the lock enabled smooth materialisation in and out of the Vortex. (PROSE: Harvest of Time)

By the Doctor
When the Doctor's TARDIS and the Master's TARDIS had each landed inside the other, the Third Doctor and each put a time lock on the other's TARDIS to prevent escape. (TV: The Time Monster)

In the New Earth System, the Fourth Doctor used the Daleks' time transporter to create a time lock that froze the Daleks and the Werelox on board the Dalek battlecraft in one moment of space and time forever. (COMIC: Doctor Who and the Dogs of Doom)

When the Doctor used the Moment at the end of Last Great Time War, the entire war was time locked. (COMIC: Don't Step on the Grass) When the Eleventh Doctor showed Alice Obiefune, the Squire, and Abslom Daak the Last Great Time War, he could only show them the time lock around it. He said the human mind did not have the capacity to fathom what it was seeing, so it appeared to them as a "big simple wall". (COMIC: Outrun)

On one occasion when Donna Noble was beating the Tenth Doctor at backgammon, he placed the board in a time lock until Donna became bored and gave up. (AUDIO: Time Reaver)

Dalek Caan overcame the lock on the Time War after making an emergency temporal shift and travelled back to the Gates of Elysium to save Davros. The process flooded Caan's mind with total knowledge of the past, present and future, driving him insane. (TV: The Stolen Earth) The only other things capable of breaching the time lock were those that were already in place, like the signal that had been transmitted back through time into the Master's mind and, on at least one occasion, very small objects, such as the White-Point Star diamond sent by to follow the signal in 's head. (TV: The End of Time)

When the Tenth and Eleventh Doctors confronted the War Doctor as he prepared to use the Moment, the Tenth Doctor noted that they shouldn't have been there as the events should be time locked. The Eleventh Doctor deduced that something let them through (this being the Moment itself). Later, the Doctor's other incarnations were able to breach the time lock to save Gallifrey. (TV: The Day of the Doctor)

By Time Lords
Rassilon, fearing the alterations to history, timelocked the time before the Time Lords, declaring the Dark Times off limits. (PROSE: What the TARDIS thought of "Time Lord Victorious") Despite this, both the Tenth, (COMIC: Old Girl) and Eleventh Doctors had made trips to pre-Time Lord Gallifrey. (COMIC: The Lost Dimension)

It was one of the Time Lords' ancient weapons, (AUDIO: Random Ghosts) used to hide their secrets and misdeeds. When Skagra used The Worshipful and Ancient Law of Gallifrey to access Shada, Romana II hypothesised that they were passing through a time lock, (PROSE: Shada) and later referred to a time lock as "Shada technology." (AUDIO: Ascension)

Matthias quarantined Time Lords infected by the Dogma Virus in time-locked facilities. (AUDIO: Ascension)

The entirety of the Last Great Time War was time locked, the edges of the time lock even tearing through the middle of planets such as Lujhimene. (COMIC: Running to Stay Still)

Gallifrey's history was protected from potential Dalek incursions by a time lock during the Last Great Time War. (AUDIO: Legion of the Lost) Nevertheless, the Daleks tried to travel back to prehistoric Gallifrey to prevent the Time Lords from evolving, (PROSE: Engines of War) and the War Doctor himself travelled back to the First Segment of the war to thwart a Dalek plot. (PROSE: The Stranger) however, the Twelfth Doctor unknowingly arrived on Gallifrey in his past in his TARDIS, which led Clara Oswald into meeting the First Doctor when he was still a child. (TV: Listen)

Following the removal of Gallifrey from the universe, it was no longer time-locked and could be reached by TARDIS at its new position at the end of the universe following its release from the pocket universe. (TV: Hell Bent)

By Daleks
Led by a new Emperor Dalek, the Daleks of the New Dalek Paradigm planned to remove Gallifrey from existence and become the new Lords of Time. They used a piece of the Eternity Clock to put a time lock around a large part of London in 2106. Once they perfected their time lock technology, they planned to use it to put temporal bubbles around other planets, making them unstoppable. However the Eleventh Doctor and River Song stole a Time Capsule from the Silents to break through the Daleks' time lock. They infiltrated the Emperor's Flagship managed to take back the piece of the clock. (GAME: The Eternity Clock)

Skaro's history was protected from potential Time Lord incursions, such as the Fourth Doctor's original mission to prevent the creation of the Daleks, (TV: Genesis of the Daleks, AUDIO: Ascension) by a time lock during the Last Great Time War. (AUDIO: Legion of the Lost) Evidently, the time lock was no longer in effect following the war as the Twelfth Doctor unintentionally arrived on Skaro during the Thousand Year War, leading to him meeting Davros as a child. (TV: The Magician's Apprentice)

By Torchwood
Another sort of time lock, created by Torchwood 3's resident genius Toshiko Sato before her death, was designed to freeze the Torchwood 3 Hub in a bubble in time. It was at the same time impenetrable but inescapable. The time lock was either shut down or damaged when a Dalek trapped at the edge of the bubble was blown up by the Meta-Crisis Tenth Doctor. (TV: Journey's End)

By Ace
At the Time Lord Academy on Gallifrey, Ace was given the planet of Talmeson to watch over. The planet was eventually wiped out by the Daleks. That was when she decided to wipe out the Daleks by time locking Skaro using an Omega device. When the Doctor found out that Ace went missing, he sent Bernice Summerfield to find and stop her. (AUDIO: The Lights of Skaro)

By the Weeping Angels
The Weeping Angels could create something that essentially functioned like a time lock by causing too many time displacements, such as the one that separated the Doctor from Amy Pond and Rory Williams in New York. (TV: The Angels Take Manhattan)

Expression
The Vist looked down upon the "time-locked races" in reference to their natural time travel ability. (AUDIO: The Forbidden Time)

Time streams
All individuals had personal time streams that were difficult and dangerous to travel into, much like a time lock; however, this only applied to the time stream of a particular individual, and it was more easy to cross. (TV: The Wedding of River Song, TV: The Name of the Doctor)