The section A & C are the same just opposites - A is left and C is right. These sections when as a whole make the unit accessable by two competing racers at the same time (right and left). The Unit can be broken down to seperate pieces for rental. However the usage changes in so far as if there are two competing racers they are going to start at the same entrance if you remove A or C and if you only have B they will start at the rear and go forward. If not competing the players run from entrance to exit one at a time.