Question Hazardous materials placards are usually shaped like: Answers Circles. Triangles. Diamonds. Explanation Hazardous materials warning placards are usually diamond-shaped. Take a FREE Practice Test Now This questions appears in the following tests: Alaska HazMat , Arizona HazMat , Florida HazMat , Hawaii HazMat , Idaho HazMat , Maine HazMat , Ohio HazMat , Oklahoma HazMat , Utah HazMat ,