Along and across the grain of wood

All trees and pieces of (natural) wood are easy to ‘chop’ with an axe, in one direction only. This downward blow is called cutting "along the grain".

Once trees have been cut into logs - they are then cut into ‘planks’ of wood, as shown.

Wood is much stronger in 1 direction, than it is in the other (opposite) direction. It is the direction of “the grain” which provides and determines the strength across the grain.

Which of these 2 scaffold-boards do you think will be stronger: 1 or 2?.

Which of these 2 arrangements do you think a karate expert would find it easier
to chop in half; A or B.

Many years ago trees used to be "chopped- down". Why do you think saws were used
Instead, once they had been ‘Invented' along the grain.