Wall
Walls are structures found on several stages in every Super Smash Bros. game in some capacity. They can cancel the momentum of a character that has been sent flying, and depending on launching speed and angle, can send that character in the opposite direction at a fraction of the knockback. Since Super Smash Bros. Melee, characters were able to tech on walls to both cancel their knockback momentum and quickly revert to their neutral falling position to act with either an aerial attack or their recovery. Melee also introduced wall jumping, a technique available only to a few characters, which allows them to jump off of walls (with mostly offscreen walls and very short walls having walljumps disabled); even if a character has no natural wall jump, they can do so during a wall tech. A bonus is awarded for hitting, but not teching walls multiple times in a short time span during a match. Samus, Link, and Young Link are capable of using their grappling tools to grab onto walls, which aided their recoveries. Super Smash Bros. Brawl introduced wall clinging, which was available to even fewer characters and allowed them to attach themselves to walls as an act of stalling. Teching, wall jumping, and wall clinging return in Super Smash Bros. 4.
All walls will stop projectile attacks and dashing characters; dashing and running characters will crash into walls and stop moving (indicated by a special animation), though they can walk indefinitely into a wall (for no practical effect). The walls on Shadow Moses Island can be destroyed by attacks, and otherwise have the same properties as regular walls.
