It was the height of the French Reolution anf three men were scheduled to be guillotined that day: a priest, a politician, and an engineer.
The priest was first. He knelt down and was saying a prayer as the executioner released the blade, which swooshed down mightily...and stopped about halfway. Stunned, the executioner declared, "This must be a sign from God. This man must go free!" And so the priest was released.
Next was the politician. He knelt before Madame guillotine as the executioner released the blade. Swoosh! And the blade again stopped halfway. The crowd was in awe as the executioner proclaimed. "God's grace has extended to this man! He, too, must go free!" And the politician was released.
Finally, the engineer was brought up. He turned to the executioner and said, "You know, if you tighten that bolt, this thing will work."