Check and X Barrels
From the Super Mario Wiki, the Mario encyclopedia
Check and X Barrels are featured in the level, Target Terror, either in midair or on the track. Their purpose is to open or close a gate. Check Barrels open a gate while X Barrels close it. Therefore, Diddy and Dixie must hit the Check Barrels and avoid the X Barrels.
Haunted Hall features a similar type of Barrel, the Plus and Minus Barrels. They are similar in that they are respectively marked with a green and red symbol. Rather than opening gates, these barrels increase or decrease the timer during each Kackle chase. The Kongs must hit into the Plus Barrels while avoiding their Minus variant. They also make the same sound effect as Check and X Barrels do when the Kongs run into one.