Here's Why The Little Black Diamonds Are Useful

The black diamonds are mainly used by construction professionals and are called truss marks. A truss is a framework that supports a building and the diamonds appear at the 48.7 centimetres (19.2 inch) mark. If you are working with a piece of plywood the diamond marks would help indicate how many spaces and supports there are. For instance, a 2.4 metre (8 foot) piece of plywood would have 5 spaces and 6 supports.