Narrative:

On takeoff, the cockpit door came open. The 'a' flight attendant closed the door within a few seconds. I make it a habit to 'shake' the door a few times before I situation down to ensure it is truly closed and locked. On this day, I did not. In the future, I will.

Google
 

Original NASA ASRS Text

Title: B737-300. THE FORTIFIED COCKPIT DOOR CAME OPEN ON TKOF ROLL, CLOSED BY FORWARD FLT ATTENDANT.

Narrative: ON TKOF, THE COCKPIT DOOR CAME OPEN. THE 'A' FLT ATTENDANT CLOSED THE DOOR WITHIN A FEW SECONDS. I MAKE IT A HABIT TO 'SHAKE' THE DOOR A FEW TIMES BEFORE I SIT DOWN TO ENSURE IT IS TRULY CLOSED AND LOCKED. ON THIS DAY, I DID NOT. IN THE FUTURE, I WILL.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.