The Keystone BOX/K 100 lintel is designed to support internal openings with 100mm wide solid walls. It features perforations along its length, which act as a plaster key, enhancing adhesion for finishes. This box lintel is engineered to bear the full load of wet masonry immediately after installation, ensuring structural stability. For optimal performance, the lintel requires a minimum end bearing of 150mm on either side of the opening, bedded on mortar for secure placement.