Hardness is a measure of how hard a material is. Some examples of hard materials are diamond, carbides, quartz, alumina, and tempered steel. Harder materials are more difficult to cut and shape than softer ones. They are also usually more brittle. Hard materials are important in industry. Common applications include knives, saw blades, and other cutting tools, abrasives (such as sandpaper), locks and safes, automobile parts, and construction materials.