From Glitch City Laboratories
Through the use of the bicycle, a player takes advantage of how map data is loaded within Pokémon Diamond and Pearl from a successful attempt of forcing the game to reload map data incorrectly.
In Pokémon Diamond and Pearl, the term 'Tweaking' or 'Holepunching' refers to when the game unsuccesfully loads nearby map data which was previously not present on the screen. Within these games maps are broken up into 32x32 squares which are only visible at any one time. When players move out of this region, the next 32x32-tile square is loaded in order to replace the tiles two areas behind them. However, when a player is moving at relatively higher speeds and in specific patterns in between the points at which extra map data is loaded, the game will fail to load the map data effectively.
This glitch is very similar to a much older glitch which only existed in older builds of the Japanese versions of Pokémon Diamond and Pearl, which was known by many fans as the "Darkrai and Shiemi glitch", as a slight bug in the map of Elite Four Aaron's room allowed the player to surf through the door and run across the blank spaces which occupy other in-game maps. As a result of this, players could not only get to nearby areas, such as the Hall of Fame room, but with meticulous planning, they could also access Fullmoon Island and Flower Paradise in order to catch Darkrai and Shaymin (whose name was at that time not officially translated into English and was simply romanized by fans as 'Shiemi'). However, after the release of later versions of Pokémon Diamond and Pearl, Nintendo had fixed the Surf through Elite Four door glitch after many players complained about becoming stuck in "the void." After a fairly long time period of disappointment from some fans of the Surf through Elite Four door glitch, a few months after English versions of Pokémon Diamond and Pearl, the Tweaking glitch was first discovered in areas such as Jubilife City and the route below Solaocean Town by performing the method described above.
When the Tweaking glitch has been performed successfully, the player will hopefully be able to travel through a black "abyss" (invisible abyss) when he/she enters a building from behind, so that he or she can access a desirable location. However, sometimes the player cannot access the correct abyss and occassionally the game may freeze. If the player wants to escape the void, however, they can use the moves Fly, Dig or Teleport if possible, enter a building or other warp.
It is also notable that Arceus cannot currently be safely obtained through the use of both the Tweaking glitch and the Surf through Elite Four door glitch because the flag that is activated when the Azure Flute (0x1FE) is obtained, is not activated without activating Mystery Gift and talking to the delivery man in the PokéMart first, however segments of the Hall of Origin have been found through the use of this glitch.
Tweaking and Void Exploring are often regarded as two completely different glitches because of the fact that graphics and collision data has to be activated after exploring the void for a player to access an area as it would appear in normal gameplay. Void Exploring by itself (if performed wisely) is safer than a complete tweaking run, as it is easier to ensure that the player does not trap his or herself so that he or she cannot escape and it is easier to ensure that the player does not save in an invalid map location or a map with no location data (such as the tentative Jubilife Gym), thus crashing the game with a black screen. When Void Exploring, crashes from invalid map data, called BSoDs (Black Screen of Death) are still possible by testing and using the Explorer Kit (this is not to be confused with a Blackout or Freeze, as a Freeze occurs when an unexecutable script is attempted to be executed, and a Blackout is a temporary absence of graphical data, caused by any number of things). If any flag is activated in-game via Tweaking, for example by first recieving the Pal Pad in a downstairs Pokémon Center area, this will also affect the player's relative map location in some way.
Requirements for the Tweaking glitch (presuming that the player wants to catch Darkrai or Shaymin)
- A bicycle in order to tweak
- Having gone underground at least once.
- Use the Step Counter application for the Pokétch (highly recommended)
- Any Pokémon with a move such as Fly, Dig or Teleport, because the player can become trapped unless they have already activated the event referring to that Pokémon (Darkrai/Shaymin), enter a warp, or save in Fake-Sinnoh.
- Surf through Elite Four door glitch
- Out of bounds
- Mystery Zone
- ---- (Area)
-  - Easier terms used by the Hall of Origin and how the the glitches are addressed.
-  - First four videos pertain to the void.
-  - An easier tweak to get into the void (also, the easiest and shortest methods on entering the void).
-  - A Youtube channel that is very useful for videos on the Tweaking glitch, as well as many of the glitches available that use the Tweaking glitch.
-  - Hall of Origin, a website dedicated to the Tweaking glitch, as well as one of the most-updated site for modern Pokemon glitches.
-  - A walkthrough for capturing Darkrai via the Tweaking glitch.
-  - A walkthrough for capturing Shaymin via the Tweaking glitch.
-  - Getting early into Hall of Fame through the Void