A checkpoint is a vertical or horizontal line (depends on the modeling direction used) in the diagram. A checkpoint has no model element attached to it; its role is to indicate timing or phasing in the model and to help manage the space of the view. Furthermore, a checkpoint can indicate some control or synchronization that is needed in the process.
Managing space with checkpoints
A checkpoint can be a handy tool for managing the diagram space. By dragging a checkpoint you can add space or remove space from the middle of a diagram without disturbing the organization of the diagram.
To create new space in the diagram...
Select the checkpoint on the diagram, drag it to the down or right, depending on the modeling direction used, by the desired amount of space and then release the checkpoint. Now the specified amount of space is added to the diagram.
To remove space from the diagram...
Select the checkpoint on the diagram, drag it to the up or left, depending on the modeling direction used, by the desired amount of space and then release the checkpoint. Now the specified amount of space is removed from the diagram.
A checkpoint cannot be moved to the up (on vertical diagrams) or left (on horizontal diagrams) over any other checkpoint.
To move a checkpoint without creating or removing space...
Select the checkpoint on the diagram, press and hold down the Shift key and then drag the checkpoint to the desired location. The checkpoint is moved to the new position without affecting the diagram.
To change the name of a checkpoint...
Right-click a checkpoint and select the Change Name option from the pop-up menu.
To translate a checkpoint...