This section is from the book "Secrets Of The Great Mysteries", by Oudini. Also available from Amazon: Secrets Of The Great Mysteries.
Referring to Fig. 3b, it will be seen that there is a special arrangement of the upper section of the long hinge. By reaching through the openings the rod can be pulled down until the round knob can be reached. This is then grasped between two fingers and unscrewed. It can now be removed. This will allow the rod to be lifted through the hinge until it is entirely removed through the top, after which the two parts of the hinge will come apart. The door can now be swung open on the hinge side without touching the side where the locks and chains are.
The performer can now step out through the opening and close the door again, fitting the parts of the hinge back into their places. Then the rod is slipped down into the hinge again and the knob screwed on the top end of it. After this the rod is raised until the knob is out of sight in the upper section of the hinge, and the escape is completed, ready for the removal of the canopy. This trick is one of the most baffling to those who do not know the secret, for everything seems so secure and solid that escape appears impossible, and the hinge would be the last place to be suspected.
 
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