The expression is widely used in deck gambling playing cards. This phrase is known to any casino employee who has to deal with customers.
Marked Cards – playing cards with inconspicuous marks that cause cheats, to recognize the suit and/or denomination.
Marks are applied in a variety of ways, including scratches on the shirt, bending the corners and other methods. Sometimes it is possible to consider them only with the help of special contact lenses.
The rules of any casino are strictly forbidden to mark cards in any way.