Used as a steel reinforcement or core in joists for prefabricated “joist and hollow block” slab systems. Manufactured with high-strength rebar in variable diameters—up to 12 mm—depending on the required load capacity. This system is distinguished by its open-web design, where the solid web is replaced by diagonal steel bars or chords that provide the necessary and precise reinforcement. The open-web configuration also results in lighter structural elements.