"Here is the proper way to roll your dice. You make sure that you have the attention of the Game Master; that it's your turn or at least your moment, and you say, 'I'd like to make a check.' The dice is [sic] still in your hands. 'I'd like to make a knowledge-engineering check to see how the door is put together.'
"You're still not rolling yet. And the Game Master ~ this is what you're waiting for ~ the Game Master says, 'All right, make your check.' Then you take the die and you roll it. You don't roll it off somewhere hidden behind your hand. You roll it clearly and obviously across the table in front of you ... in your general area (you don't throw it across the table), but somewhere, where the result of the roll will be obviously plain to anyone nearby; particularly the Game Master. With the die sitting there on the table, you look at the number."
I grew up playing cards with relatives who had lived in the 1920s and 30s, in the backcountry of Alberta and Saskatchewan, who could still remember a time when if you were caught cheating at cards, knives emerged and people were hospitalized. In the 70s, when I would play with these people, they would make clear, unrestrained references to this practice, deliberately suggesting to my young and as-yet-unmolded thoughts that counting the number of peg holes on the cribbage board, or the way I held my cards when playing poker or bridge, mattered ~ in the way that it matters that you don't touch a red-hot burner or walk in front of a moving car. That is, moving a cribbage peg was an act of considerable tension, as we all took pains not to fuck up.
I'm not suggesting that we should cut out the hearts of people who hide dice behind their hands, or snap the dice up as soon as they are rolled, saying whatever number enters their dear little brains ... but when I did first encounter this behaviour in the early 80s, connected with role-playing, I was flabbergasted that players thought they could get away with this incredibly duplicitous shit. And I was not restrained when I made me feelings about this clear.
I could not have guessed that this, and not civilized behaviour, would become the norm. It is the sort of thing that rouses the ancestral Tory in me to say something like, "These are children who were obviously not beaten enough as children by very strong farmers."
Suffice to say, if a player were to do this at my table today, I would warn them firmly, but politely, never to think of doing it again, and never to roll a die without first getting my okay. And then, if the player did it again, any time within a year of beginning in my campaign, that player would be bounced from my game, my residence and my whole fucking life so fast that they'd only know it as their shoes, their bags and the rest of their shit was hurled after them.
Because if a player will do this in your game, that same player won't hesitate to steal five dollars off your bureau, or a die out of your collection, or task a roommate to rob you of your computer so that he can cover his drug habit or some fine he has to pay. People who show their character by this sort of flag are awful, loathsome scum, waiting for the eventual day when the social structure lands on them with a force that routs them into permanent, often incarcerated obscurity.
I say, help society do that.