A priest, a politician and an engineer were scheduled to be executed late in the French revolution. It has to be "public", and people are tired of all the bloodshed, so a crowd of spectators is forcibly rounded up.
The priest is brought up to the guillotine and lays down on the table. The executioner pulls the cord and the heavy steel blade descends ... then shudders to a stop in the middle of the track. The executioner is a very smart guy (which is why he is pulling the cord, rather than laying on the table) so he proclaims, "This is a sign from God, that the life of this priest should be spared." The priest is set free to the delight of the cheering crowd.
Next the politician is brought up and laid on the table. The cord is pulled, and the blade again shudders to a halt in the same place. The executioner proclaims "The grace of God is extended even to this politician." and the crowd goes wild with joy!
The engineer steps up last and says, "You know, if you tighten that bolt, this thing will work."
Image Credit: A Truth Soldier