Moon clipping is a common method of reaching out of bounds areas that involves tilting Mario's hitbox into a wall just as he collects a Power Moon. The Power Moon must be uncollected, meaning this is a one-try trick in speedruns. However, save file backups can allow players to attempt these clips multiple times outside of a speedrun context.
To perform a moon clip, one will need to execute a backflip while facing away from the wall, and cancel the backflip animation by performing a cap throw toward the wall just as Mario collects the Power Moon. Mario's hitbox tilts sideways when he performs a cap throw during a backflip in this manner, and collecting the moon forces his hitbox upright. However, if his hitbox is tilted into a wall, Mario will be half-bounds after he is forced upright, allowing him to be moved fully out of bounds after the moon cutscene is over.
There are a few notable moon clips that have been made applicable for speedrunning:
Each of these clips requires a slightly different timing for the inputs, since the moon positioning and timing is different for each.