This is a quick demonstration of how "Napier's bones" work for multiplication of a large number (up to nine digits in this demo) by a one-digit number. A description and explanation of "Napier's bones" can be found on Wikipedia.

Type an integer up to 9 digits long, then use the drop-down to select the row. Napier's Bones have 9 individual stick with the multiples of the top number. This arrangement allows the user to add the diagonals of the row highlighted to produce the product. Read the Wikipedia article above for more information.

Thanks to Prof. Wright with with his app on I made some minor changes to his work.