Why do they tie their thumbs and don't use handcuffs?
&quot;A normal zip or cable tie is borrowed. A participant firmly cables the performers two thumbs together, making it impossible for the performer's hands to separate&quot; (wonderwizards.com).
So my understanding is that by pinning the thumbs together, separating the hands becomes impossible and thus, minimal hand movements restrict leverage to pull on the rest of the bindings
https://www.wonderwizards.com/lesson/blacktie2018