The Explorer Kit can be used anywhere in the Sinnoh region, except inside buildings and other structures, to instantly access the Underground. The player also cannot dig through elevated structures such as bridges.
When used, it asks the player to save the game and indicates that DS Wireless Communications will be turned on. It then transports the player from their current location to the corresponding spot of the Underground's tunnels.
The Explorer Kit includes all the basic tools used when adventuring, mining, and collecting in the Underground. When certain tools are used for the first time, notes describing their functionality are shown to the player.
Hammer: The hammer is used to dig through walls to find spheres and treasures. It makes a bigger impact on the wall than the pickaxe, digging up several tiles at a time; however, this causes the wall to collapse at double the speed. The wall will collapse after 25 hammer hits.
Pickaxe: The pickaxe is also used to dig through walls. It makes a smaller impact on the wall than the hammer, causing fewer tiles to be dug up at a time. This causes the wall to stay strong for longer before collapsing. If anyone else is mining nearby, a pickaxe will appear on the player's screen wherever the other player hits on their screen. The wall will collapse after 49 pickaxe hits.
Map: The map is displayed on the top screen and shows all of the Underground as well as spots to dig into the walls. There are six independent sections of the labyrinth, each accessible from different places in Sinnoh. In terms of vendors and mining treasures, the areas are equivalent. When in multiplayer mode, the map also shows the positioning of the other players in the Underground.
Radar: The radar locates all treasure, spheres, and traps in the Underground. By touching the touch screen, the radar will appear and locate all treasure, spheres, and traps near to the player. If a sparkle is revealed on the floor using the radar, it is either a trap or a sphere; traps have white sparkles, while spheres have gold. If both are hidden in one spot, a trap is found first, then a sphere. If the sparkle is in the wall, it is a bulging section that can be mined.
The Explorer Kit also comes with containers to carry Spheres and Decorations (aka Goods). Spheres are the currency of the Underground. They can be sold to vendors that appear in the Underground. These explorers are stationary and will only rotate in place. Each of the three types accept spheres, and will trade the player either goods, traps, or treasures.
Goods are generally known as the items that can be used in the Underground to decorate the player's Secret Base, such as dolls, chairs, and tables. Goods can also be purchased in the fourth floor of the Veilstone Department Store, or obtained from Mr. Goods after completing certain requirements. The rarity of the goods is determined by the value of the Sphere being asked for. For example, an Iron Beam is worth a Prism Sphere 9 and a Pink Dresser is worth a Green Sphere 54. This concludes that the Pink Dresser has a much higher rarity than the Iron Beam.
Due to a glitch, the Explorer Kit is not usable when the player stands two tiles to the right of the Bug Catcher at the western entrance to Eterna City. Instead, a message will appear: Rowan's words echoed... <player>! There's a time and place for everything! But not now. This glitch is present in Pokémon Platinum but not Pokémon Diamond and Pearl.
Unlike other Key Items from Pokémon Diamond, Pearl, and Platinum, the Explorer Kit is not present in the data of Pokémon HeartGold and SoulSilver. However, like all Generation IV Key Items, it is present in the data of the Generation V and VI games.