The clamshell double umbrella (Bard Clamshell Septal Umbrella, USCI Division, C. R. Bard, Billerica, MA) was developed to allow closure of septal defects, both atrial and ventricular. The device and delivery system and the techniques for implanting the device in atrial and ventricular defects are described in detail. Although fractures of the arms supporting the umbrellas in some patients have lead to modification of the device, the early experience in clinical trails are encouraging.