Structured Surface BRDF Reciprocity: Theory and Counterexamples

A device adapted to travel up, down or horizontally on the side of vertical walls, having means to adhere to said wall, power means and traction means. In one form of this invention a magnet is employed to cause the device to adhere to a ferrous wall, the magnet being spaced a slight distance from said wall. Rubber tires are provided on the wheels for traction. In another form of this invention rubber coated magnetic wheels are used. In another form rubber coated magnetic treads are used. In another form of the magnetic climbing devices the power means may be omitted and the devices are adapted merely for climbing down on ferrous walls, they being drawn downwardly through the force of gravity. In another form the climbing device uses suction means to enable it to cling to a wall. This device can be used in air or under-water. In this form a pump is used to create a low pressure area between said device and said wall.