This month, four San Francisco 49ers defensive backs simultaneously -- and very intentionally -- grabbed and held the New Orleans Saints receivers they were covering. The clock showed eight seconds to halftime, and the 49ers gladly took a 5-yard penalty from referee Jerome Boger rather than give the Saints' explosive offense a real chance to score a touchdown.

The Saints settled for a 26-yard field goal on the next play, validating the 49ers' strategy and prompting the obvious question: Why don't teams do that more often? And what's to stop a team from deliberately and systematically breaking any rule when the markoff is more palatable than the potential outcome?

As it turns out, the NFL's extensive rulebook has it covered.

Rule 12, Section 3, Article 2 prohibits teams from committing "successive or repeated fouls to prevent a score." If they do it again after receiving the required warning, according to Article 3 of the same rule, the act is to be declared "palpably unfair." (For those seeking further clarification, "palpably" means "obviously." I had to look it up, too.)

In such instances, referees are instructed to award the yardage a player would have reasonably gained -- including a touchdown if applicable. They also return the lost time on the clock and have the option to eject the player(s) responsible.

Those instructions existed before the 49ers took down the Saints' receivers and will continue to apply moving forward. They allow for a benefit of the doubt in one instance, but protect against a team routinely holding, tackling or otherwise committing intentional penalties as a substitute for actual defense and as a means of premeditated strategy.

We've seen similar instances before, and so has Boger -- most notably at the end of Super Bowl XLVII. As you might recall, the Baltimore Ravens decided to punt from their end zone while clinging to a five-point lead over -- yes -- the 49ers with 12 seconds remaining. Ravens coach John Harbaugh ordered a play that called for his punt protectors to intentionally hold the 49ers' rushers, giving punter Sam Koch a better opportunity to kill time prior to stepping out of bounds for a safety.

There was no downside to that decision -- the Ravens would either give up two points or have to punt again after a minimal markoff for a holding penalty.

Inexplicably, Boger did not call holding at all. But if he had and thus the warning would have been given, the Ravens would not have been able to repeat the play to take off more time. If they did it a second consecutive play, they would have been (presumably) penalized for a palpably unfair act. The clock would have been restored to its original time.

You might shake your head at the idea of the NFL accounting for intentional penalties, but the league has no choice but to assume that competitors will seek every edge they can. Manipulating rules isn't the NFL's idea of a good time. (No jokes, please.) And in some cases, a single specific act judged to be palpably unfair can reverse the outcome of a play or even a game.

"Goal-tending" a field goal -- jumping to knock the ball away from the crossbar -- is named as a palpably unfair act in the rulebook. So is holding a substitute on the sideline until just before the snap or shortly thereafter, giving him a free run to the ball because he is likely to be unaccounted for.

The NFL rulebook also uses this umbrella to address random (or seemingly random) turns of fate. If a player is knocked down on the field of play by, say, a photographer who is out of position, the play is to be ruled palpably unfair and the assumed yardage is to be marked off. And the commissioner has the right to overturn the outcome of a game because of a palpably unfair act that wasn't adjudicated adequately by the referee.

Rare is the time when a non-player impacts a play in real time. (A notable exception from college: The 1982 "Band is on the Field" game.) And there are no confirmed instances of the implementation of the palpably unfair clause, even if you could argue that it was warranted when Pittsburgh Steelers coach Mike Tomlin ended up on the field during a kick return in a 2013 game against the Baltimore Ravens.

On the other hand, you could assume all kinds of rule manipulation by NFL teams if the palpably unfair limitation wasn't in place. The 49ers used their opportunity at a perfect moment, but it's not something anyone can build a long-term strategy with.

As always, the chart lists the NFL's Week 11 referee assignments filtered by penalty frequency in their games this season.