Compression marks are formed when a tool is forcces into a softer material.

• A. Formed when a tool is dragged across a surface
• B. Formed when a tool is heated
• C. Formed when a tool is hammered into hard metal
• D. Formed when a tool is forced into a softer material

Answer: (D)

Compression marks arise when a tool is pressed into a softer material, causing the substrate to yield and take an imprint of the tool’s surface. The resulting mark is a negative impression where the tool’s edges and textures are captured by the deformed material. This is what distinguishes them from other tool marks.

If a tool is dragged across a surface, you get striations from sliding contact, not a pressed-in imprint. Heat can alter surface features but doesn’t define a compression mark—the key factor is the plastic deformation of a softer material under pressure. Hammering a tool into hard metal would produce impact or peen marks rather than the clean compression impression seen in a softer substrate.