You're supposed to be able to finish all of the levels and get normal endings without the need for artefacts such as knives. The artefacts are just optional, make you a better player and allow you to get special endings.
Well, it is almost impossible to solve the final notebook and get the normal ending without using the black key shortcut, even with the magnet and personal calculator at your disposal. Well, unless you use Cleany to open it, but still.
No. Last time I did it, I packed some "NUTS" Chocolade Bars and went the passageway past Mr. Mix. The one that leads to a fork in the path with a vending machine in the middle and two large classrooms on either side.
