Here is what each signal means:

• Hoist: The workman is telling you that he has finished hooking the bucket onto the crane, and it is ready for you to lift.
• Bridge Travel: The workman is demonstrating the direction that you need to move the bucket toward the concrete form.
• Lower: The workman is signaling that you have the bucket positioned above the formwork, and can begin lowering it.
• Stop: The workman is telling you to stop lowering the bucket. He can begin pouring in the concrete.

Normally, the crane operator communicates with only a few people on the site. However, there is one signal he must obey from anyone, and that is the stop signal. There may be an obstacle in his path, or a problem on the site that he isn't aware of.