One of the challenges of being a tank, whatever war you're in, is the fact that your sights are limited. This even applies for Tanks as huge and as sophisticated as the German Koenigstiger in the World War 2. The axis have always faced difficulties agains soldiers from the allied companies when it comes sticky bombs, or attachable mines.
The Krupp war factory in Essen, Germany, tried to tackle this problem. One of the ways is to invent the Zimmerit coating for their tanks. What is Zimmerit?
As the picture above, you can see how there are parallel horizontal lines/grooves in the body of the tanks. This coating aims to create an area surface that is not smooth, so that sticky bombs or magnetic mines simply fall of due to their weight and rattles of the tank. This coating was applied in many of German's battletanks from August 1943 - September 1944 (around the times of the Ardennes expansion).
This invention is one of those things that i like to call ingenious. Its simple, yet its application is very very useful. It creates that ideal distance between the bombs or mines to the hull. Imagine King Tiger II's thick armor added with this coating. Scary!