It is more difficult to explain how this device is used than it is to use it.

Click on a thumbnail image for a larger view.

Here the rod and movable clamp have been moved to the end position and the total height of the bowl, including the chucking spigot and foot is measured. The fixed clamp is tightened.

In this photo, the movable clamp has been moved under the beam and tightened. This captures the height so that the rod can be moved to the center position.

This photo shows the rod moved to the center position. The fixed clamp is then locked.

This photo shows the movable clamp moved atop the fixed clamp and locked. The length of rod below the beam is the total height of the bowl.

Here the caliper has been set to the height of the foot and chucking spigot. The fixed clamp has been loosened and this measurement is transferred to the gap between the fixed and movable clamps. The fixed clamp is then locked. The rod length below the beam is now the outside height of the bowl excluding the foot and chucking spigot.

This photo shows the movable clamp moved up to touch the fixed clamp. Both clamps are now locked.

This final photo shows the device placed on the bowl. The fixed clamp has been loosened to allow the rod to slide upward. The fixed clamp is then locked. The space between the two clamps is the thickness of the bottom of the bowl. As turning proceeds, the gap will show the remaining thickness of the bowl excluding the foot and chucking spigot.