Soil nails are long, slender steel bars that are inserted into the ground to provide stability to slopes, excavations, or retaining walls. They are typically installed at an angle and are grouted into place, creating a reinforced structure that helps prevent soil movement and erosion. This technique is commonly used in civil engineering and construction projects, especially in areas with challenging soil conditions. By reinforcing the soil, soil nails can support various structures, making them a cost-effective solution for enhancing safety and stability in construction sites.