Linked portals (development versions only) are a powerful feature which make it possible to connect two separate areas of a map via the floor/ceiling or one-sided linedefs, allowing the player to see, shoot, and even move seamlessly from one area into another. They are used similarly to two-way portals, apart from the fact that you can pass through them. They can be used to create 3D architecture and room-over-room effects, with very few limitations.
# Class Trig Description
358 Ext -- Apply linked portal to like-tagged ceilings
359 Ext -- Apply linked portal to like-tagged floors
360 Ext -- Linked portal anchor line for special 358
361 Ext -- Linked portal anchor line for special 359
376 Ext -- Apply linked portals to like-tagged lines
377 Ext -- Anchor line for special 376
Refer to Zarkyb's linked portals tutorial for in-depth information on usage.