An activity that spans between two points in a network diagram. It has no duration of its own but derives one from the time difference between the two points to which it is connected. In the precedence diagram below the hammock (H) stretches from the start of activity B to the finish of activity E.
Few contemporary scheduling software packages offer hammock as a feature. Instead they allow a hierarchy of activities and summary activities. This can achieve something very similar to hammocks but is not as flexible.