A haunch plate is a steel or metal plate used in formwork to create and support haunches (sloped or thickened portions) at the junction of walls and slabs in box culverts. It is placed at the corners or junctions where the wall meets the base slab or deck slab, providing a mould for the haunched section of concrete. The haunch plate supports the shuttering panels and resists the pressure of wet concrete, ensuring that the haunch retains the correct shape, alignment, and thickness. It also helps transfer loads safely to supporting props or beams and prevents bulging of the formwork at corners.