Juice-marking - The marks are only visible when anyone is properly trained to read through the marks. No filtered sunglasses are required, Whilst glasses can be used to make it much easier to place these marks. c) It is possible to observe pot control if you have a mediocre/drawing hand. https://edwinjzofs.theisblog.com/6508958/5-easy-facts-about-marked-cards-contact-lenses-described