Friday, June 25, 2004


Some things I've been learning this week in my training. No, I'm not training to work at a casino or anything - it's statistics and math.

Crooked Dice

With so much money riding on the roll of a die it's no surprise that crooks try to influence the outcome.  Here you can learn all about the methods the cheats use to win your money...

Crooked dice are not a recent development. The Indian Hindu Sanskrit, Mahabbarata, the first documented reference to dice, mentions crooked dice and examples have been found in ancient sites in the Orient, South America and the Middle East.

Dice that are fair are known as straight or square dice, perfects or levels. Terms for crooked dice are numerous and there are a number of methods for gaffing dice. Crooked dice do not behave in the same manner on every throw but they do change the odds and so are known as percentage or P.C. dice.

A dice mechanic will substitute crooked or gaffed dice for the real ones and can quickly switch them back once they have gained their advantage. Slight of hand may be used or the switch will take place when the dice are out of sight.  Crooked gambling houses used to employ stickmen for Craps who would switch the dice when signalled. Today the major casinos are honest and have no reason too cheat. An expert switcher will almost be impossible to spot. If you suspect a switch has taken place then you could examine the dice yourself. Remember the dice you are playing with may not be the dice that started the game and cheats will switch the dice back and forth as it suits them. A cheat may even let another player take his crooked dice away, just writing his loss off as part of his scam. This means there could be crooked dice in circulation that no one is aware of.

Craps is where the money is so crooks and cheats target this game the most. Passers are crooked dice that favour passes and not the 7, or craps on the come out throw. Missouts are crooked dice that favour the 7 and not the points.

Loaded dice or weight will be heavier on one side. The extra weight may be lead, gold or platinum so it only takes a small amount to change the odds. The weight is often placed nearer one corner or edge rather than at the centre of one face. Transparent dice do not prevent loading because the actual spots can contain the weight. Check if the spots are deeper on some sides than others, although this is no guarantee because a well made gaffed dice will look straight and even. To test for loaded dice simply repeatedly drop the die in a glass of water. It should sink and if a particular number always faces up the die is loaded. The pivot test is one where you hold the die between your thumb and finger by diagonally opposite corners. If the die is loaded it will tend to turn downward as you lightly hold it.

Floats or floaters don't have extra weight added but weight taken away so they become lighter. They are hollow inside and the gap is placed off centre to bias the dice. They are known as floaters because they will often float, with the hollow side up, when placed in water.

Tapping dice or tappers are dice with a hollow dumb-bell shaped chamber inside. The hollow chamber is filled with mercury. When the mercury is in the end of the chamber near the centre of the die it is fair. But when the cheat wants the die to be biased he will tap the die so the mercury runs to the other end and weight one corner. Some tappers use the same principal but with a weight that slides up and down the chamber on a fine wire. These may have a ratchet mechanism to hold it in place until the die is tapped and may have a rubber bumper to prevent any noise. Obviously these dice must be opaque. Tappers are not used often because of their unreliability. To test for these, tap the die on all it's corners and use the loaded die tests.

Shapes are dice that are not true cubes. Shapes may be convex or concave on some sides or edges or a side may have been shaved down.

Bevels are shapes with one or more convex sides. These dice will be more likely to roll off the convex sides and on to a flat one.

Suction dice have a concave side which can create a slight vacuum when rolled on a hard flat surface. On a rough surface the dice tend to stop on the concave side when a flat side would keep on rolling. These dice favour the opposite side of the concave one.

Trip dice have edge work and flat sides. Dice are manufactured with different types of edge. There are different ways to machine the edge of a die and if all the edges are machined the same way the die is fair. Trip dice will have differing edges. They tend to wear after use and need to be replaced by the cheat quite often.

Cut-edge dice are trip dice that have an edge shaved at an angle of 45 degrees while the others may be at 60 degrees which effects the roll.

Raised-edge dice are trip dice with a lip on some sides. These sides have more surface area and also grip when rolled on cloth.

Dice with razor-edge work have different edges. Dice can be razor edged on some sides and turned or rounded on others so the die will roll off the rounded edges and grip on flat ones.

Split-edge or Saw-tooth edge work is serrating some edges of the dice with tiny cuts. The idea is these edges will grip. The bias is hard to ascertain and these dice are said to be worthless to a cheat.  


Bricks or flats are shapes that have one side shaved down so the four adjoining sides are made smaller and have less surface area. The shaved side and its opposite face will be the more likely outcome. Six-ace flats will favour the 1 and 6 sides and work against the shooter in a game of Craps. Flat passers are a pair of dice cut down to favour 3-4 and 6-1 so totals of 4, 5, 9 and 10 occur more often (point numbers in Craps). Barred dice is another term used for these.

Bevels can be held together or pressed on to a flat surface. If they rock back and forth you know the die's face is convex. Try running your finger over the sides of the die feeling for lips or edges. Remember to check all sides of a die to determine if it is a shape. There are devices used by casinos called micrometers that measure the sides of dice extremely accurately. Sometimes shapes and loaded dice are combined, with both defects so minute that spotting them is difficult. Different methods of shaping and gaffing dice can also be combined to produce such things as razor edge convexes, bevelled suction shapes, etc.  An obviously mis-shaped or loaded die is said to have very strong work that won't pass in fast company.

Raised spots are supposed to cause the dice to roll off that side. The spots aren't finished properly and these are used by amateur cheats. They can be easily felt and are not as effective as other crooked dice.

Capped dice are shaved down on some sides and then have the material replaced by a layer of material that matches in look but differs in elasticity. The dice tend to bounce off these sides and settle on one not doctored. The join should be invisible all though wear and heat may show it up after time. Use your finger nail or something sharp to feel the resiliency of all sides. Liquid capping is the painting of dice with a solution that dries to get the same effect. This isn't worth doing because the substance becomes sticky in players hands and picks up dirt.

You will often see dice players blowing on the dice for good luck. Another way to cheat is to paint sides of the dice with a clear sticky substance which can be activated by the moisture in the cheats breath causing the dice to have a tendency to stick to the throwing surface.

Slick dice are polished on some sides while the other sides are roughened. This is supposed to make the dice slide to a stop on the smooth side and roll off a rough one. This bias is negligible but is hard to spot because even straight dice can become rough after a lot of use.

Bristles are dice gaffed with a pin. The pin is inserted into the centre spot of the 5 side, only slightly protruding, and will hold if rolled on a cloth or baize surface. They are known as bristles because pig or horse bristles were used. It is an extremely old method of gaffing dice. Outmoded and not used by professional cheats because of the likely hood of being discovered.

Mis-spotted dice with duplicate numbers on opposing faces are called tops and bottoms. Other terms for these dice are tops, mis-spots, horses or tees (T's). A gamblers term for these is busters. These can easily be identified simply by examining all the faces of the die. Remember all opposing sides must add up to 7. These dice are not as instantly recognisable as you may think because only three sides of a die are visible at any one time.

Double number dice have two sides of the same number, double deuces will have two 2 spots and no 5. A pair of dice with duplicate sides of 1, 5, 6 and 3, 4, 5 will never produce a total of 2, 3, 7 or 12, the only numbers that can lose in Craps. High-low splitters are marked twice with 1, 2, 3 on one die and 4, 5, 6 on the other. These produce a lot of 7's and a crooked house would switch them in when some one has made a heavy bet on the field in a Craps game. Door pops are a pair of dice that only ever come up 7 or 11. One die is spotted with 6's and 2's the other is all 5's on every side and only a complete idiot would fall for these. Games that require high numbers to win, like Backgammon or High Dice, can be played with high number dice that have two 4's, 5's and 6's. Low number dice have two 1s, 2s and 3s.

Electric dice are metallic on one side or have metal slugs in the spots on one side.  These are used with an electromagnet under the playing surface. Greedy Chuck-A-Luck operators sometimes use them under the counter or chuck cage and special Craps tables were manufactured to incorporate the magnet. Electric dice are not as commonly used as they once were due to the fact that many dice players carried a magnet to test for them. If a die sticks to a magnet then without doubt it is crooked. Gambling venues that use electromagnets are known as juice joints or wire joints. These are not strictly speaking percentage dice because when the magnet is on the outcome is certain.

Crooked dice may be unconventionally spotted so a cheat can differentiate between them and a set of straight dice when switching them back and forth from a game.  

If playing dice for money you should play with transparent dice to reduce the chances of using crooked ones. Casinos always use these dice and today's major casinos are respectable, professional operations and have no need to cheat. Don't play with strangers but rather stick to a friendly game with people you know well and trust. Should you ever find that you are in a crooked dice game the best advice is to cut your losses and take no further part. Even if you are positive the game is rigged the situation could rapidly turn ugly if you were to accuse some one.
Casinos don't take any chances when it comes to profit so they don't use just any dice when thousands of dollars are riding on a roll.

Casino dice are called perfect or precision dice because of the way they are made. They are as close to being perfect true cubes as possible, measured to within a fraction of a millimetre, manufactured so each die has an absolutely equal chance of landing on any one of its six faces.

Casino dice are specially hand made to within a tolerance of 0.0005 of an inch. The spots are drilled and filled with material that is equal in weight to the material removed. Usually sides are flush and edges sharp.  They are predominantly transparent red but can come in other colours like green, purple or blue.  Spots are usually solid but a number of different designs can be found.


It is believed all casino dice should have the same conventional arrangement of faces and spots.  They're right handed so that if the 1-spot is face up and the 2-spot is turned to face the left then the 3-spot is to the right of it with all opposing sides adding up to 7.  If the 1 spot is face up then the 3-spot runs diagonally up from the left and the 2-spot runs diagonally down from the left.  A different orientation of the spots is sometimes used on crooked dice (made to look like casino dice) so a cheat can differentiate them from a set of straight dice.  

Since the 1970's, and the move to corporate owned casinos, it has become more and more common for casino dice to have serial numbers printed on them. The number is 3 or 4 numeric digits, possibly with letters and dashes, usually printed on the 6-spot but can be found on any face except the 1-spot. This number denotes the issue and is used to prevent them being switched for crooked dice. Another security check sometimes used is having key letters printed on the underneath of spots which can only be viewed by looking through the transparent die.  The casino's name, sometimes location, and/or logo will often be printed on the dice too using a metallic foil.  The 1-spot usually bares the casino's name while the 2-spot may have the logo.


The most common size today is 3/4 inch but the size can vary with 5/8 inch and 11/16 inch the next most common sizes.

Casino dice were made of cellulose nitrate, starting around the 1920s, but sometime around the 1950s the manufacturers switched to cellulose acetate which is more durable. Very old casino dice have often started to crystallise and will have turned yellowish around the edges. This crystallisation is caused by age and exposure to moisture and ultra-violet light.  A completely crystallised die will disintegrate if pressure is applied.

Casino dice can be readily bought. However many cheap casino dice are in fact rejects that haven't met the manufacturers standards or used dice that have been cancelled by their casino. Both rejects and used dice will have been defaced in some way.

Manufacturers call rejects culls. These are factory marked with a hot pin in the centre of the 4-spot or hot stamped with a number of 'X' or star symbols or just simply stamped with the word "VOID".  Some manufacturers stamp a gold "O" onto the four spot.


Used dice may be bought as souvenirs from many casinos although some refuse to let them go. When a die is taken out of play it will be cancelled. It could be that a hole is drilled through it or a crescent or circle is pressed into one side with a vice.  Sometimes a gold bar is hot stamped on the six-spot.  A sharp pointed metal scribe is often used to press a small shallow mark into a face.  Some older dice were scratched or had a date or initials marked on them.  By state law Atlantic City casinos must drill all the way through their used dice. 


If you want true perfect dice then pay the extra for a stick. A stick is a number of dice that are still in their sealed pack as delivered by the manufacturer.



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