I just called Hilton to ask about using my Citi free night certificate on an existing booking. I asked about cancelling the original and making a certificate booking instead.

The representative told me that there isn't such a thing as a certificate booking and that I should just present my reward certificate to the hotel front desk in lieu of payment. She explained that a certificate booking is nothing more than a normal cash booking, guaranteed by credit card, that is eventually settled with the certificate instead.

Has anyone ever done this before? I'm asking because it sounded unusual to me.