Time lock

A time lock was a mechanism whereby an event or series of events was rendered unreachable by time travel. It was thought impossible to pass through a time lock, but this was proven false; Dalek Caan did so, but at the cost of his sanity. (TV: The Stolen Earth)

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 this time lock had slipped. (TV: The Web of Fear)

By the Doctor
In the New Earth System, the Fourth Doctor created a time lock to trap the Daleks and the Wereloks outside of the TARDIS. (COMIC: The Dogs of Doom)

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)

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)

By Time Lords
In ancient times, the Time Lords used time locks to hide their secrets and misdeeds. When Skagra used The Worshipful and Ancient Law of Gallifrey to access Shada, Romana hypothesised that they were passing through a time lock. (PROSE: Shada)

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

Davros suggested once that Emperors and Time Lords had attempted to breach a time lock, but failed. 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 Rassilon 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. A comment by the Moment's interface implied that it was she herself that let them through. (TV: The Day of the Doctor)

By Torchwood
Another sort of time lock, created by Torchwood 3's resident genius Toshiko Sato, 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 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)

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