An abacus is a mathematical aid that was developed from its forerunner, the counting board, which predates both Greek and Roman civilizations. The standard abacus consists of a series of vertical rods with sliding beads. A cross beam separates two beads at the top of each rod, known as the heaven beads, from five at the bottom, known as the earth beads. Using a cigar box as a base, it is easy to make an abacus of your own.
List of Items Needed
 Cigar box
 Ruler
 Hammer
 Nail
 11 wooden skewers
 77 beads
 Craft knife
 Wood glue
 Stiff cardboard

Stand the cigar box up on its back panel so that the hinge is facing up. Measure the length of the box and divide the result by 11. Use the pencil to draw 11 evenly spaced marks one halfinch below the hinge.

Use the hammer and nail to gently punch a small hole through each of the pencil marks. Turn the box onto its front and make a second set of marks and holes directly opposite the first set.

Lay the box flat with the lid open. Push each skewer through from the back of the box to the front. As each skewer appears inside the box, thread seven beads onto it before continuing to push it through the hole at the opposite end.

Use the craft knife to trim any excess wood from the skewers so they fit inside the box neatly. Add a drop of wood glue at each end to ensure they remain in place.

Cut an inchwide strip of cardboard to the exact length of the inside of the cigar box. Lay the strip flat across the skewers inside the box and mark the position of each skewer. Cut halfinch slits along one side of the card at each mark.

Push two beads from each skewer to the top of the box and the remaining five to the bottom. Fit the cardboard crossbeam a third of the way down from the top of the box so that each skewer fits into the correspondent slit. Your abacus is now ready for use.
Tips and Warnings
 Use a nail with a diameter slightly smaller than that of the skewers, otherwise the holes will be too large.
 If you do not have a cigar box, you can hold the skewers in place with popsicle sticks glued at the front and back with another set acting as the crossbeam.