A couple weeks ago, we were lucky enough to have Sandy, our woods expert, come out and walk the perimeter of the property with all of us- which, at the time, was 8 of us! We were quite a funny trail of ducklings, scurrying through the woods behind Sandy, keeping our heads down looking for barbed wire and learning how to recognise the blaze marks on a tree.
So, why is it important? For many reasons, some being that when you
have a woodlot, you need to know where your neighbour's property ends
and where yours begins, so you don't help yourself to that really nice
birch just across the line without knowing it. 
Also, in a time before GPS and property lines, and the absence of fences, the "blaze" (that is, the hatchet notches and paint on a line of trees, marking the property borders) was often the word on property borders, and still is! In the case of future property disputes, the blazed line through the woods is taken as right, even if it differs slightly from maps. It's very important, therefore, that the blaze be maintained: It's essentially like maintaining one's fence.
...It's maintaining your non-fence!
