Dice must be carefully made so that each cube is perfectly balanced on all six sides. If not, some sides of the cube will come out more than others.
Currently, most dice are made of plastic, either by hand or machine. After the cube is formed, a certain number of dots are punched into the die faces.
Then each hole is filled with a drop of paint that weighs exactly the same as the plastic that was removed to make the hole. In this way, the six sides of the die remain balanced, no matter how many holes each face has.
The "loaded" dice - the ones made for cheating - contain an extra weight inside one of their six sides. When a loaded die is rolled, the extra weight helps the cube often fall on the heavier side, so the side opposite that side will show up more often than it should.
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