If you don't already have the black key in your belt, then yes, that is the only way, but things are much easier now. There are now blue and yellow paper notebooks found in random classrooms that can each be shredded into several papers, saving you time from having to collect other trash to make a trail for Cleany. Remember to have at least 1 lockpick with you (there are also uncommon steel lockpicks now, but they cannot be stored in the belt like the black ones) to open the locker with the black door key (remember which locker it is). One more thing, WHEN YOU SAVE ITEMS TO YOUR BELT, ALWAYS REMEMBER TO PRESS F WHILE THE BELT IS OPEN, OR ELSE YOU WILL LOSE EVERY ARTIFACT YOU RECENTLY COLLECTED IN YOUR CURRENT RUN WHEN YOU RESTART, EXIT, OR BEAT A LEVEL!!! NEVER FORGET TO SAVE YOUR BELT ITEMS WITH LEFT ALT+F!!!