Using an analog or digital clock, remove the batteries/unplug to stop the clock. Set it on a three digit or four digit code of a combination lock.  For example, if the pass code to the lock is 1134, stop the clock's time at 11:34.  The players should notice the clock has stopped and figure out that it is a code. If the clock is not on a wall, put a note on it 'do not touch' so they won't move the time on it and lose the code. 

Props needed for this scenario:

• Clock on the wall / on a desk. 

• Locked box, suitcase, traincase, etc.