The Very Fabric of Time and Space - often referred to as the Very Fabric - was a place which connected all possible eventualities.
The Sixth Doctor could make tears in the Very Fabric inside his TARDIS control room. He once created a tear to send the Wishing Beast from 1965 Salford to an asteroid in the distant past. (AUDIO: The Vanity Box)
In the 1930s, the Very Fabric was stretched thin around the town of Darkholmes. Numerous individuals fell through the Very Fabric and ended up in alternate versions of the town (such as Daakholmes) or on other planets (such as Hyspero). (PROSE: Fellowship of Ink)
When the Onihr interrogated Fitz Kreiner for the secrets of time travel, Fitz mentioned the Very Fabric along with various other time-related phenomena he had encountered during his travels with the Eighth Doctor. (PROSE: Trading Futures)