Small black diamonds on tape measures mark 19.2-inch intervals, dividing a standard 8-foot (96-inch) span into five equal spaces.
These symbols serve as practical reference points for positioning floor joists and roof trusses designed for 19.2-inch spacing.
While standard wall framing typically uses 16-inch spacing on center, the black diamonds allow quick layout without extra calculations.
Understanding various tape measure symbols helps ensure accurate measurements and alignment across diverse woodworking and building plans.