Part I: Card Game Cheating · CARD MARKING METHODS
Corner Marking / Nail Nicking
How it works
Corner marking (also called “nail nicking”) involves using a sharpened thumbnail or small blade to create small nicks or cuts on the corners or edges of cards. The cheater grows their nails long and strong enough to perforate coated card stock. Different patterns of nicks indicate different values - a nick on the top vs. side, two nicks together, a nick on the corner, etc. Advanced nicking involves “localizing” marks so they can be read whether the card is right-side up or upside down. The marks can also be made on poor cards to identify when opponents are bluffing.
Where it appears
Poker, private games
On the record
Nail nicking is a time-honored technique described in detail in historical gambling literature. It requires no tools beyond a well-grown thumbnail, making it accessible to amateur cheaters.
Detection & prevention
The paid halfHow a monitoring room catches corner marking / nail nicking, and what stops it recurring — written for the desk, not the reader.
Detection · 30 words
Prevention · 31 words
Published as a detection reference for surveillance, compliance and gaming-operations professionals. Thresholds and tuning are set by the property. Nothing here is instruction — the method is described so it can be recognised.