Who's Knocking? It Must be Spirits!

At Least, That’s what your Audience will think when your Wand beats a RAT-TAT-TAT on your table!
1) But we know it’s not spirits, don’t we. Because, this is what we’ve done to make the wand rap out its weird message.
2) The two candlesticks are important!  A fine black thread is tied to candle (A), and runs through an eyelet on candle (B).  Thence, the thread runs off-stage to a hidden assistant, who pulls it gently when necessary. The wand rests on edge of tray and its end ties on the thread. Thread runs through eyelet on candle (B). eylet on table and a third eylet on floor to hidden assistant in wings.
3) If you wish to dispense with a hidden assistant, tie the other end of the thread to a chair and press body gently against it.