Transdimensional portals were the transport used by the Threllips. Each required a projector, tertiary signals and aligned sub-space modifiers to work. It allowed the transport of objects or information.
On 11 July 1982, Vengorr and Thon were sent to Earth to set up a transdimensional portal to allow the Threllips to invade. The Eighth Doctor distracted them and reprogrammed it. When Vengorr and Thon went through it, they were transported to one of the moons of Mordelius Prime. (AUDIO: Living Legend)
The Time Fracture acted as a transdimensional portal. (WC: 14683 UNIT Field Log)
During the Last Great Time War, when the Valeyard erased the Daleks from N-Space, save for the Dalek Time Strategist who used a dimensional portal to flee into the multiverse. (AUDIO: The War Valeyard) The Dalek Time Strategist emerged in an alternate universe on a parallel Skaro from a similar portal created by the native Davros, allowing the Time Strategist to escape. Wiring itself into Davros' portal, the Time Strategist was able to turn the alternate Davros into a workable facsimile of the Davros from N-Space and resurrect the Dalek Empire from its multiversal counterparts. (AUDIO: Palindrome, Restoration of the Daleks)