Final answer:
The rule to always identify and mark utility installations before starting excavation work ensures safety and prevents damage to utilities.
Step-by-step explanation:
When excavating at a site where utility installations are present, one crucial rule you should always follow is to ensure the identification and marking of all utility lines before beginning any digging or excavation work. This precaution is vital to prevent damage to the utility installations themselves and to safeguard the workers from potential hazards, such as electrocution or gas leaks, which can result from accidentally striking a utility line. It's also important to maintain a safe distance from the marked utilities as prescribed by local regulations or utility companies when digging. The use of precision instruments and careful planning as part of today's controlled excavations make it possible to safely conduct excavations even in areas with utility installations.