The returner can signal a fair catch when returning a kickoff or punt. On a fair catch, the returner asks for a unhindered attempt at catching the kick. To signal a fair catch, the returner will hold his arm up into the air.
On a fair catch, the return ends immediately when the returner catches the ball.
PRO TIP: On a fair catch, the returner is not required to catch the ball. If the returner decides not too and then touches it, it's treated as a fumble.
After a fair catch, the offense starts with the ball at the spot of the fair catch was signaled.
Fair Catch Interference
Players on the kicking team are not allowed to interfere with the returner's attempt at catching the ball. A penalty called Fair Catch Interference is given to a player that touches the player.