The Double Tap gesture on Apple Watch Series 9, Series 10, and Apple Watch Ultra 2 allows for easy access to various functions.Double Tap selects the main button in the app you're using and can control the Smart Stack on the Apple Watch face.Multiple tasks can be performed with Double Tap, including interacting with callers, managing messages, controlling media playback, and more.To enable and customize Double Tap, navigate to the Gestures settings on your Apple Watch or iPhone.