One on the Gantt charts timeline, when we highlight the desired task, small circles to the left and right side of that task will appear. Dragging to the circle of another task and dropping it there will create a dependency between these two tasks. We can only perform a single drag and drop operation at a time, and each task (the one we start at and the one we end at) has two sides. This means there are four kinds of visual links (in a form of an arrow).
Four Types of Links
As mentioned - every task on the Gantt chart has two significant sides - to the left and to the right. These symbolize the Start and End Dates. Therefore, by linking two tasks (below referred to as the Task A and Task B) we can expect four possible combinations:
This means that when Task A starts, Task B will also start.
When two tasks are connected this way and task A is moved to the left, task B remains unchanged. When Task A is moved right and exceeds the Start Date of Task B, then Task B will also be moved to the right in order to start at the same time as Task A.
When Task B is moved to the left, it will never go further than the start date of Task A. If Task B is moved right, Task A remains unchanged.
When Task A starts, Task B will immediately finish.
In this type of dependency, when Task A is moved to the right, if its Start Date exceeds the End Date of Task B, B will be also moved right. Moving Task A to the left changes nothing.
When Task A finishes, then Task B starts.
Moving Task A to the right will also move Task B, as long as Task A's End Date is moved up to or ahead of Task B's Start Date.
Moving Task A to the left has no effect on Task B. When Task B is moved to the left, it will not go further than Task A's End Date. Moving it to the right has no effect on Task A.
When Task A ends, Task B also immediately ends.
Moving Task A to the left changes nothing. However, if Task A is moved further than Task B's End Date, Task B will be moved in order to retain the dependency (and to end at the same time).
Moving Task B to the left further than Task A's End Date will automatically move Task B's end at the same time as the end of Task A. Moving Task B to the right has no effect on Task A.
To change the link type between two tasks you can also click on the link and select a different one in the "Type" section.