Genaille-Lucas rulers (also known as Genaille's rods) is an arithmetic tool invented by Henri Genaille, a French railway engineer, in 1891. The device is a variant of Napier's bones. By representing the carry graphically, the user can read off the results of simple multiplication problems directly, with no intermediate mental calculations.
Enter a desired number to be multiplied by any number from 1 to 9 in the input field at the top. Then, look at the index for a section of desired multiplier. Starting from the rightmost ruler, look at the top digit in multiplier's section. An inclusive arrow on the left points numbers to the next ruler, so just follow those until you reach the index. The result of calculation is all the digits in that path, read from left to right. Not so complicated after a few tries ;]