Hi everyone, here are a few more Mailbag questions this week and I'm happy to answer them. (Read the latest chat recap here ). I received a pair of questions from readers who want to know about what constitutes a stiff-arm move by a running back vs. an illegal hands-to-the-face penalty.

Randall N. from Tahlequah, Okla., wrote:

"Why is the runner never called for illegal use of hands to the facemask when they stiff arm a tackler but it is 15 yards if the offensive player face mask is even touched? I have seen plenty of tacklers have their head shoved way back as a result of a stiff arm (move)."

And Walt G. from Altoona, Pa., wrote:

"Why is it illegal for linemen to put their hands in an opposing player's face, but a ball carrier is allowed to do this, often in a violent manner (aka, a stiff arm)?"

Hi Randall: Actions by the runner and the defender trying to tackle the runner are the same. Both can use their hand on the facemask of the opponent either to ward off the tackle or, if you are the tackler, in an attempt to make the tackle. Neither can grab the mask and pull, twist nor turn it. If they do, it is a personal foul and a 15-yard penalty. The interpretation is different in interior line play. If either the offense or defense pushes the facemask back pinning back the head of an opponent, it is a foul unless the hand is immediately removed. Lastly, a defender cannot jam the head of an eligible receiver, period.

And Walt, I think this answers your question but you bring up a good point -- this has been a point of emphasis in the NFL for the last two years, and the rule says that the runner may use an open hand to the face to ward off a defender but he cannot use it forcibly to deliver a blow. If he does, it is a personal foul.

Jeremy M. from Cedar Park, Texas, wrote:

"On two occasions I thought Troy Polamalu sacked Kerry Collins in Week 2 (Steelers vs. Titans). First Collins had to chase down a bad snap and Polamalu tackled him for a huge loss. Second was when Polamalu leaped over the line and stuffed Collins for a loss on the QB sneak. On the stat sheet for the game Troy Polamalu is credited with ZERO sacks. How come?"

Hey Jeremy, good question. You are only credited with a sack if it is a designed passing play. The errant snap is not considered a passing play and the QB sneak is a running play. Therefore, no sack for either of Troy's tackles.

Greg W. from Kamloops, British Columbia, Canada (Go Seahawks!) wrote:

"Dear Mr. Pereira: With 1:55 remaining in the third quarter of the game between the Colts and the Giants, Peyton Manning was set under center, but backed away from the line and called for a substitution, without using a timeout. A tight end left the field and was replaced by a wideout. At what point does the offense become committed to running the play without movement on the line caused by a substitution triggering a penalty such as a false start or illegal substitution? Thank you for the consideration of my question."

You're welcome, Greg! The only players who can't be substituted for in that situation are offensive linemen who are in a three-point stance. A legal substitution can occur any time before the snap regardless of whether the QB is under center or in the backfield. The QB is free to back away from the center after assuming a position to receive a hand-to-hand snap. Keep in mind -- any sudden movement by the QB or any departing player is a false start.

Rich G. from Bel Air, Md., wrote:

"Why don't you make the officials full-time, year-round, instead of part time people who have other full time jobs? That way they can get specific training (mental and physical), so these controversial calls (Ravens vs. Bengals) won't happen in the future. That call and the tripping call changed the entire flow and took momentum away from the Ravens. Granted, there were plenty of mistakes (turnovers) made by the Ravens, but the game should be decided by the players -- not the officials. Has there ever been any thought of putting younger people on the field to call games? Thank you."

Hi Rich: Making officials full time will NOT eliminate incorrect calls. NBA referees and Major League Baseball umpires are not perfect and make their share of mistakes, yet they are full-time. Football is a once-a-week game and not conducive to full-time officiating. It is an avocation for football officials. There aren't minor leagues or developmental leagues. NFL officials have established successful careers outside of football and to ask them to give that up would be ludicrous. If you tried to make all NFL officials full time you would lose at least a third of the staff and that would be a disaster. Younger officials on the field? Do you know who makes the most mistakes? Is it the experienced guys that still have good judgment or the young guy who has never worked games with this type of speed? I will give you a clue -- nothing beats experience. That being said, there does come a time when an official has to move on.

Thanks for all the mailbag questions, everyone! Keep sending them in and I'll talk to you next week in our Tuesday chats on FOXSports.com at 1 p.m. ET