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 to 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.

If you want to learn all about the techniques of switching dice then take a look at the Shooting/Rolling page where you'll find links to pages where the methods are described

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 something very heavy like 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.