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The first track that was laid was the spiral that connects the outer and upper lines. Since grades were considered to be a serious problem, an attempt to reduce the grade was made by tightening the spiral as much as possible. There is only 8" of clearance between the bottoms of the ties to the bottoms of the ties above. Even so, the grade is 5.2% on the 4 foot diameter spiral. The track is supported by horizontal braces that provide support only at the rail joiners so that the support structure doesn't add any thickness beyond that of the tie strips. Later, a Masonite strip was added inside the vertical supports to provide a "crash fence" to prevent derailments from falling toward the center of the mountain and landing on the floor.