This is the default operation mode. It corresponds to the Arrow tool 
.
This mode can be restored at any moment by selecting this tool or by clicking with the right button of the mouse.
Selecting graphical objects
Click a graphical object or link to select it: this selection is identified by selection squares (handles) appearing at the corners and on the sides of the object.
Double-click to open a dialog box.
This dialog box is used either to create the description of the object or the link (in this case the fields are empty) or to modify it, or simply to display it.
Single selection
A single click on an object makes a single selection: all the previously selected objects (identified by selection marks) are not selected anymore.
Extended selection
Several objects can be selected by holding the Ctrl key, and by clicking successively the various objects to be selected.
Rectangle selection
All the objects contained in an area of the work space can be selected by clicking the window background (with the left button), then by dragging the mouse while holding the left button: a rectangle is drawn until the mouse button is released. All the objects entirely contained in this rectangle are selected simultaneously.
Full selection
The Select all option from the Edit menu is used to select all the objects simultaneously.
Deselection
Click the background of the model (outside of any object) to deselect all objects.