The Markable Mark (2013)

This never led to the loss of any chickens, so the woodcutter learnt that it was a rule of the game that two marks on a tree – or even more than two – meant the same as one: a marked tree was none the less marked for having more than one mark on it. If the forester changed his mind again (so he wanted the tree felled, after all), he would just make a third mark beside the cancelled first one, thus:

Sometimes, as if in playful spirit, he would accomplish the same end in a different way. The woodcutter (who was actually quite a clever man – and on top of that, he was often accompanied by his 10-year old son, as he went round the woods) thought that if he squinted very hard at it he could just see a sort of logic in this: it seemed that the third mark cancelled the second one, meaning that the interior of the first mark was not marked after all, so that it was after all a good effective mark, signifying that the tree had to be felled.

Source: www.markability.net