Allow your spectator to completely examine a case that is divided into three compartments. Have him screw three metal nuts and bolts into the case. The nuts and bolts are not gimmicked in any way. The spectator locks his own finger ring onto one of the end bolts. Slide a transparent cover onto the case so that it is impossible to remove the ring. However, when you cover the box briefly with a handkerchief, the ring has magically jumped onto the middle bolt.