Final answer:
Cranes must be within 1 percent of level grade and have a firm footing for safety and stability during operation.
Step-by-step explanation:
Cranes must be uniformly level within 1 percent of level grade and located on firm footing. Ensuring that cranes operate on a level surface is critical for maintaining the stability and safety of the equipment. The requirement of being within 1 percent of level grade is key to preventing accidents and equipment failure. A firm footing is equally important as it provides the necessary support to handle the loads that the crane will be lifting, and prevents sinking or settling that could lead to uneven weight distribution and potential tipping.