Once felled, the trees are lopped into 'logs' cut into two or more sections called 'foot logs' for the lower part of the trunk and 'upper logs' for the parts where the branches have grown. From the outside to the inside, the cross section of a log allows you to observe the bark, the sapwood (an imperfect and unusable wood), the perfect wood (which will be used - as here in planks - and sorted according to its properties) and the core (to be eliminated for certain works).