What material is used below standards to aid in levelling and squaring?

The correct answer highlights that sole boards and base plates are used below standards to assist in leveling and squaring a scaffolding structure. These components serve as the foundational elements that distribute the load of the scaffold over a larger area, ensuring stability on uneven surfaces. By providing a level platform, they help in achieving the proper alignment of the scaffold, which is crucial for the safety and effectiveness of the structure.

Sole boards are typically wide pieces of timber placed under vertical scaffold standards, while base plates provide a flat surface to optimize weight distribution and prevent sinking into soft ground. Together, these components play a vital role in ensuring the overall integrity of the scaffolding.

The other materials mentioned do have important functions within scaffolding, but they do not directly contribute to the leveling and squaring process in the same manner. For instance, shoring frames are used mostly for support and stabilization but not specifically for adjustments to leveling. Scaffold planks are primarily for providing walkable surfaces and load-bearing capacity, while cross bracing serves to enhance lateral stability and prevent sway but does not assist in establishing a level base.