A billet is a small slip of paper commonly used in mentalism and spiritism performances to facilitate the illusion of mind reading or thought transference. Participants write down thoughts, questions, or drawings on these pieces of paper called “billets,” and the billets are then folded or sealed. Through billet reading, the mentalist knows the participants’ thoughts. Through sleight of hand, psychological techniques, or mechanical methods, the mentalist performer secretly views the content without the audience’s awareness. Billets are considered a cornerstone of mentalism due to their portability and versatility, enabling performers to create highly personal effects and impactful routines using nothing more than bits of paper.

The use of billets dates back to the early days of spiritualist séances and has evolved into a refined art form within mentalism. Techniques such as billet switches, center tears, and peeks allow performers to secretly read or replace the billets while maintaining an air of mystery. Despite advancements in electronic gimmicks, many mentalists regard billet work as a pure and direct method for creating compelling performances. Mastering billets requires skillful sleight of hand, misdirection, and an understanding of audience psychology, making it a revered practice among mentalists for its ability to produce seemingly impossible feats with minimal props.