What is the hand signal to raise the boom of a mobile crane?

The hand signal to raise the boom of a mobile crane is represented by a thumb up with a clenched fist. This signal is widely recognized in the crane operation community as it clearly indicates to the crane operator that the boom should be raised. Using a clenched fist with the thumb pointing upwards creates a distinctive signal that is easily visible from a distance and helps prevent confusion or miscommunication between the signal person and the crane operator.

In the context of other signals, an open palm facing up is typically associated with a different action, such as a "stop" signal. Similarly, two fingers pointed upwards may convey a different command or instruction that might not specifically refer to raising the boom. A hand waving upwards could be misinterpreted due to its less specific nature, as it doesn't provide a clear and direct signal like the thumb up with a clenched fist does. Thus, the chosen signal is the most effective and standard for raising the boom on a mobile crane.