On Library walk, you will see many different cement blocks with years on each one. Find the years listed on the puzzle card.

Each cement block that coincides with the years on the puzzle has something different than the others. Look down below. Can you see through the holes on the bottom? Not all of them? Why?

The red disc on each cement block gives you a single digit for the four digit code:
2010, the fourth circle below is red, so the number for 2010 is 4.  2000 = 2; 1997 = 5; 2004 = 1.  The code to unlock the lockbox is 4251. Open it to find the word HOPE.