From Tekkenpedia

Wall Jump
Command	b,b,u/b
Stance
Damage	Varies
Hit Range	Varies
Properties	Varies

Wall Jump is a secret move that can be performed by any character in Tekken 4 and all games after that. In order to initiate Wall Jump the character's back must be against a wall or like object. Damage, Hit Range and properties are dependent on the character of which is performing the Wall Jump. Most Wall Jump manueveres can be guarded against and reversed.