Note: This page is taken from n.wikia.com.
(As written in the N in-game help)
While airborne and near a wall, press jump to launch off of it. This skill can be used to quickly climb "chimney"-type spaces.
Walljump is a maneuver that can only be consistently performed by a ninja
To execute this maneuver, one must simply jump at a wall and press the jump button again as they touch the wall. This should cause the ninja to ascend even higher.
This is one of, if not the most basic maneuver in all of N. To master (or at least become decent at) N, one simply needs to understand how to walljump effectively.
Below are a few of the most used of maneuvers that involve the usage of a wall.
Wallclimbing[]
Wallclimbing is defined as using a wall (or any set of tiles with appropriate height) to reach a certain height.
Most beginners find wallclimbing exceedingly difficult because they tend to just mash the jump button as quickly as possible.
This is wrong and gets the ninja nowhere. Instead, after building up a good speed and jumping at the wall, the player ought to hold the directional key that is towards the wall they are climbing up (if the wall is to their right, they must hold right, etc.), and tap jump only the instant when the ninja hits the wall. This causes the ninja to jump up, and holding down the directional key causes the ninja to move towards the wall while jumping. So, when the ninja touches the wall again, the player needs to hit jump and repeat until they've reached the desired height. For an example of effective wallclimbing, it's recommended to take a look at any decent score on 27-2: pwny, where the ninja wallclimbs up the right wall.
There is an additional trick associated with unit-width columns (chimneys/chutes), such as those on 29-4: pinchy. Highscorers move up those with great speed, which doesn't require any special methods. The player has to simply jump against any wall of the chute, let go of any directional keys, and mash the jump button. The ninja should blast up the shaft with great speed!
It should also be noted that if the player wallslides before jumping off a wall, then the resulting jump can be smaller than normal.
Wallsliding/Wallhanging[]
When one's falling towards the ground and is near a wall (or any tile for that matter), they simply have to press the directional key that is towards the wall. The ninja will hang on the wall and slow down significantly. If they player doesn't do anything, the ninja will continue hanging on the wall until it hits the floor. To stop this process, the player must simply hit jump, or press the directional key opposite to the wall. This is often used to prevent death from falling from a lethal height. However, as the ninja slows down while hanging, most highscorers are able to make the ninja wallslide for a split second and then fall normally again. If timed properly, the ninja will still survive the deadly fall, but will have wasted minimal time. To do this, one ought to simply press the directional key towards the wall (while you are already beside said wall), then immediately let go and press the opposite key. An example of this would be 15-0: all about thwumps, where highscorers use this to survive the pestilent drop on the left to get down and get the gold.