From the massive videogame
Portal 2
Description
Test subject description: Place the bookend with the orange entrance on the left side of a row of books, and the bookend with the blue entrance on the right. The "effect" is that your books (or DVDs, games, disks, tapes, etc.) will stand upright on your bookshelf. (At least, they should do it. If not, maybe you did it wrong...?)
Okay, this is what all bookends do! But these portal bookends look like a test subject passing through a portal from one side and exiting from the other side. This is neater!
Call it a portal experiment!