There are two holes in both of Zaku's hands. Zaku can manipulate sounds waves and pressure to release power sonic blasts from the holes on the hand. Zaku is the only known ninja to have utilization of this device. One way to counter this technique is to cover up the hole. When Zaku tries to use the jutsu the sound will get stuck and soon implode his arms. This is how Zaku lost both of his arms against his fight against Shino.