In "Card Manipulations" by Jean Hugard, he mentions a way to catch your arm spread cards using a hat on page 43. Hugard also mentions using a "bag fake" so you could turn your hat upside down to show that the cards are not in the hat. What exactly is a bag fake? Is it just a regular bag you put in your hat to catch the cards? Thank you for your help.

I don't know what a bag fake is, but it may be a secret section in your hat that is open at the start, you spring the cards in and then close it and show the hat empty