Which situation results in a legal fair catch signal?

A legal fair catch signal is made to indicate to the kicking team that the receiver intends to catch the ball without the risk of being tackled. The signal must be clear and distinct to avoid confusion on the field.

When a receiver lifts one arm straight above the head, it is a universally recognized signal for a fair catch. This action demonstrates the receiver's intention to make a fair catch, allowing them protection from being hit, as the kicking team must give the receiver an opportunity to catch the ball unimpeded.

In contrast, other actions such as raising one hand without the full arm lift or waving both arms do not meet the specific requirements for a legal fair catch signal as defined by the rules. For example, simply raising one hand or waving both arms may not convey a clear intention of making a fair catch, leading to potential risk for the player. Therefore, the correct signal must be an arm lifted fully and clearly above the head to be considered valid.