The bomb that the BLU team needs to push on pl_badwater.
Payload
On Payload maps, the BLU team must escort a cart full of explosives through a series of checkpoints and into the RED team's base within a certain amount of time. BLU team members move or "push" the cart by standing next to it - the more people near the cart, the faster it moves. Any RED team member standing near the cart will stop it from venturing further. If a BLU player does not push the cart after 30 seconds have passed, the cart will start slowly moving backwards until it reaches a checkpoint/BLU spawn or a BLU player stands next to it again. The cart works as a Level 1 Dispenser for the BLU team (and disguised enemy Spies) to restore health and ammunition to those pushing it.
Gameplay
Payload maps may or may not be split into multiple rounds. Some maps traditionally have one-way routes from the BLU team's side, sometimes closed off until a specific point is taken. Maps such as Gold Rush, Hoodoo, and Thunder Mountain are split into three stages that the BLU team must advance through and win. Stages one and two have two checkpoints and stage three has three checkpoints (two for Hoodoo), counting the final point as such. The Badwater Basin and Upward maps have a single round with four checkpoints, counting the final point as such. Advancing the cart to the next checkpoint gives the BLU team extra time. Advancing it to the final point moves the map onto the next stage. When the cart reaches the final point on the final stage, the Payload cart will explode killing anyone standing too close to it and destroying the RED team's base as well, thus symbolizing the BLU team's victory.