Which is a common signal for "stop" during crane operations?

The common signal for "stop" during crane operations is typically represented by waving an arm back and forth. This gesture is widely recognized in the construction and rigging industries as a clear and concise indication that the operator should halt operations immediately. The back-and-forth motion is highly visible and can easily be seen by the crane operator from a distance, which is crucial in maintaining safety on job sites.

The other signals mentioned may have different meanings in various contexts. Raising one arm overhead is generally associated with a signal to "raise" or "lift," while extending both arms out horizontally usually signifies a "slow down" or "workplace condition" alert. Pointing to the operator with both hands does not conform to standardized signals and may lead to confusion rather than clarity in a high-stakes environment, where precise communication is essential for safety.