Just because you can't climb straight-up a wall doesn't mean you can't climb up at all. Corner-Teching with Back Ejects allows an Assassin to rise up fortress or neighborhood corners via "tick-tacks" or sequenced walljumps. Extremely contextual, like much of Unity -- but useful when possible. This broad tactic exists in the old games (AC1-Rogue) of course, and as most of us know, would have been more easily done, particularly in AC1-Revelations.