A horizontal crossbar perpendicular to the rods separates the abacus into two unequal parts. The beads above the crossbar are known as heaven beads or upper beads, and those below the crossbar are called earth beads or lower beads. Counting on abacus is done by moving the beads up and down the rods. The beads are moved with the help of the thumb and the index finger. Moving the bead towards the reckoning rod is used for addition and moving away for subtraction. Lower beads are moved up by the thumb finger and for all others bead movement the index finger is used. Before using the abacus make sure that all the beads are in the neutral position representing zero. This can be done by placing the thumb and the index finger on the horizontal crossbar lightly and moving it across from left to right. This has to be done every time before starting a new calculation.