A nut and bolt, with a tiny piece of plastic pipe, and a plastic tube are shown to the spectators. The magician threads the nut on the bolt, trapping the plastic brass pipe. The whole unit is placed into the tube and the cap is placed on top. The magician now makes a few "magical" gestures and the cap is taken off the tube, and the contents are poured out onto the table. To everyone's amazement, the nut is no longer threaded on the bolt, and the plastic tubing is now free.
Everything is then examinable.
This is a magnificent close-up effect.
This method does not use invisible thread.
This is an economy version of the Nutty Nut, a regular version of this made in Aluminum and Brass is also available.