A wood leveling ruler, or screed, is a crucial tool for plastering, ensuring a smooth and level surface. Made from durable hardwood and usually 1 to 2 meters long, it has straight, smooth edges. To use it, first prepare the wall by cleaning it, then apply plaster evenly with a trowel. Hold the ruler firmly with both hands against the plastered surface and move it in a sawing motion to level the plaster, filling low spots and removing excess. Check the surface with a spirit level and adjust as needed. Once the plaster sets slightly, smooth out imperfections with a float and let it dry completely. Keep the ruler clean after each use and work in sections for better control on large surfaces.