The A-B cart is a rollercoaster-like object seen in the video game Below. It's name comes from the term "Point A to Point B", referencing it's use of bringing objects from one room to another.
The cart is a metallic gray minecart-like device with no wheels and a screen inside of it. The cart is fastened to a long line running throughout the hotel and low/lower/lowest levels so that it may go where it pleases.
It appears on Floor 240, 540 and 5,540. On Floor 240, it is used as a prop briefly seen running throughout the facility to startle players. On Floor 540, the player must travel through the facility inside of it. On Floor 5,540, it's used to travel to various peaks in the mountain-like structure.