This section is from the book "Secrets Of The Great Mysteries", by Oudini. Also available from Amazon: Secrets Of The Great Mysteries.
The method of escape is as follows: When the bolts are passed out through the holes in the cover, the solid bolts shown in Fig. 4 are not used, but those shown in Fig. 3 are substituted. In this bolt the head "C" can be removed from the bolt "D." This is the head on the inside of the box, and it will be noticed that it is never seen by the committee, so no suspicion is aroused. The outside of the bolt is exactly the same as Fig. 4.
Fig. 3.
The heads of these bolts are removed by means of a small wrench which has been concealed until this time, and the bolts can be pushed out until they fall to the floor, allowing the cover to be lifted and the escape made. After the escape it is necessary to return the box to its original position, which requires a little more thought. The original four bolts, Fig. 4, are placed in the box, but the nuts are removed and kept outside. A long string is tied through the hole in each bolt and passed out through the four holes in the sides of the box, leaving the bolts on the bottom. Now the ends of the strings are passed out through the holes in the cover and a small stick tied to the end of each string to prevent it from slipping hack into the box while working on the others. The cover is now placed on so that the holes come opposite those in the box, and the bolts are drawn up and out through the sides of box by means of strings. Now the strings are removed, the nuts screwed on, and the cotter pins placed through the holes in bolts. As soon as the strings and extra bolts have been concealed the cabinet may be removed, showing the box still bolted and the performer outside of it.
Fig. 4.
 
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