Ask the Official: November 13, 2010
Is there a penalty if a player of the non-kicking team jumps up and hits the crossbar during a field goal attempt? – Glen W.
The situation that you describe requires some further clarification. If you are asking whether there is a specific penalty for a player just jumping and hitting the crossbar while the ball is in flight the answer is no although the officials could cite the player for unsportsmanlike conduct if the ball was in the vicinity of the uprights and/or the cross bar and the officials felt that the action was intended to move the goal posts so that the kick would miss.
If on the other hand, there was a player stationed in the end zone and he jumped in an attempt to bat a ball down as it crossed the crossbar and he made contact with the ball or the bar, he would incur a 15 yard penalty because, as is noted in rule 12-3-1 s, "Goal tending by a defensive player leaping up to deflect a kick as it passes above the crossbar of a goal post is prohibited. The Referee could award three points for a palpably unfair act." As a result, you will not find anyone in the NFL attempting the strategy you appear to suggest.