First, you have to apply masking tape on the leg, even where you need the checkered paint.
First, you have to trace all the vertical lines.
It's easier when the horizontal ones aren't done yet, because you need to place all these lines around the leg.
And they aren't parallel to each other.
Because the base is larger than the top.
It's a bit tricky but once you get it, it's easy to do.
Good news : horizontal lines are parallel to each others. ;-)
Now all the lines are on the aera you need to be checkered, you need to put some pencil to see the checks.
The penciled squares will be removed and painted in the new color.
After using some sharp tool to cut the squares that have to be removed, you can see the checkred aera take place.
Red undercoat, et voilà...