Double Color Prediction
Sorcier Magic
In fact, once the plaque is removed from the envelope, the public can notice that the latter contains two bolts fixed in the two holes corresponding to those chosen by the public! The envelope is empty and the magician can unscrew a bolt or two to prove that they are authentic. Provide the two metal plates, a question mark to apply to an envelope and all the bolts to perform the effect.
Easy to do, you will demonstrate your divination skills.
Envelope not included, video instructions attached.