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Mar 04, 2026

The Secret Meaning of Black Diamonds on Measuring Tapes

Most people know a measuring tape is used to measure lengths and distances. But have you ever noticed the small black diamond symbols that appear at regular intervals along the tape? These markings are not decorative—they serve a very practical purpose in construction and carpentry.
What Are the Black Diamonds?
The black diamonds, also called truss marks or black truss indicators, are usually spaced 19.2 inches apart. They help builders indicate where to place floor trusses or joists when dividing an eight-foot span into five equal parts. This spacing allows for efficient use of materials while maintaining structural integrity.

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