The original version (repeated in this instructable) consisted of sticks (bones) with numbers marked on them, but that's not so portable.
The process can, though, be repeated with pencil and paper.
In school, this method is suitable for classes of most ages who are getting to grips with multiplying larger numbers.
In the UK, KS2 and upwards.
Step 1: The grid.
For instance, if you are multiplying 748x43, you need a grid of 3x2 squares.
Draw diagonal lines across the grid (top-right to bottom-left), extending them to below the grid (see the examples in the images).
Write your numbers outside the grid (in the templates, I have drawn dotted-squares to show you where).
If you are not used to using the grids, or are just too lazy to draw them yourself, you can use the templates I have added to this Instructable.
The large sheet, with every size of grid on it, is a resource I created for my maths class, some of whom have poor motor skills, so can't draw straight lines without help.
Step 2: The easy bit.
Multiply each digit on the top row by each digit on the side column. This can mean doing quite a few calculations, but they are all simple.
If the result of a calculation has two digits, the "tens" digit gets written above the diagonal line, and the "units" digit gets written below it. For instance, 6x7=42, so write the 4 above and the 2 below (4/2).
If the result of a calculation is only one digit, write a zero above the diagonal line (2x3=6, so you write 0/6)
(You would not normally do this in coloured ink, but I have used it for clarity.)