Snapping Angles

I spotted a classic yellow wooden folding ruler tucked beside a metal toolbox. Its brass pivot rivets were dark with age, but the joints looked completely functional. I planted my boots on the shelf grain and gripped two overlapping slats, working the hinge outward. The brass detent gave a crisp, mechanical snap as it locked flat at a clean ninety-degree angle. I unfolded a third section and cantilevered the arm out over the edge of the shelf. Even suspended in midair, the wooden slat held its line without sagging a millimeter. Those brass pins lock in with serious precision.