Related Clues:

• One of 36 on a piano
• Legend; vital
• One may be passed in class
• "The Star-Spangled Banner" writer Francis Scott
• A student may pass it
• It helps one remember something
• Bottom-of-map info
• Decoding need
• A or B, but not Y or Z
• Deadbolt unlocker
• Money? There's some in nanotechnology
• Letter school returned
• Quickly written letter
• A little letter which isn't the fifth?
• Important access tool