Ohio State and Michigan are currently 2 out of 13 FBS teams to use a decal reward system on their helmets. Both teams started this tradition in the 60s, but have different philosophies for earning stickers, and what the meaning is behind them.
Video available on YouTube: https://youtu.be/PjC2Yc_PLsM
Credit:
"ESPN Sticking to Tradition
How helmet decals tell the story of Ohio State and Michigan"