All of the following apply to hazmat placards EXCEPT:

Placards are used to warn others of hazardous materials. Placards are signs put on the outside of a vehicle that identify the hazard class of the cargo. A placarded vehicle must have at least four identical placards. They are put on the front, rear and both sides. Placards must be readable from all four directions. They are 10 3/4-inches square, turned upright on a point, in a diamond shape. Cargo tanks and other bulk packaging display the ID number of their contents on placards or orange panels.