A Gavel pivoted between two blocks on a large board is displayed. The gavel is shown to swivel freely, and drops under its own weight..
Yet the performer can cause it to rise, and knock in a ghostly fashion, to answer questions, do simple maths, or act as a lie detector etc. The gavel is completely under performers control at all times.
Clever mechanical prop, made in wood, this can be used under all performing conditions.