The tumblewheel is a moveable fence post used to create mobile one-wire fences for the purpose of rotational grazing. Typically used for electric fencing, the insulated central hub enables the line to maintain power while the fence is being moved.
The tumblewheel was invented by Taranaki farmer W.A. Chesswas, and is produced and marketed by the Gallagher Group of Hamilton, New Zealand.
References
Tumblewheel Wikipedia(Text) CC BY-SA