The Shell Jump is one of the most common tricks used in Super Mario Maker. There are many variations of the basic shell jump.
How It Works
Throwing a shell towards a wall at the peak of Mario's jump will cause the shell to rebound off the wall and land under his feet. When Mario throws a shell he is not able to interact with it for ? frames. This means he needs to be at least 2 blocks from the wall in order to bounce off the shell.
When Mario throws the shell, there is a 2-3 frame window for it to land underneath Mario's feet.NoteWhen Mario is close to a wall, there is a 3 frame window. While when Mario is further away from a wall there is only a 2 frame window. The timing for shell jumps as Super Mario in the New Super Mario Bros. U game style is 2 frames later than every other style.