You notice that a lady in the audience is wearing an elegant ring and suggest a swap to her. You get the ring as a loan, she gets the contents of your coin purse. The lady puts her ring on the table, you tip the contents of your coin purse onto the table.

Put the ring in the coin purse. Shake the purse, the ring rattles. Then you fold a piece of string, which has been checked by a member of the audience, and lay it across the coin purse. The ends of the string hang down over the edge of the coin purse, they can be seen all the time and, in addition, are held by the lady. The middle of the string is situated above the purse's opening. Now push the middle of the string into the purse with a ballpoint pen, a magic wand or a playing card.
The lady pulls the string, it comes out of the purse with the ring threaded on it, although the lady has been holding the ends of the string in her hand all along.
The ring has evidently penetrated the string. The ends of the string have been visible all the time. The ring has not been prepared, It's a normal piece of thin, strong string. The penetration takes place practically in the hands of the participants, everything can be checked immediately. The ideal way to start off any ring or coin routine. A stunning effect, on its own or combined with other micro tricks. Finally, you return the ring and ask the lady to put the coins back into the coin purse.