Text and logical elements (symbols, black boxes, etc.) have insertion points. These are displayed using a small filled rectangle. Graphical elements have element points (e.g. start and end points). These are displayed using a small unfilled rectangle.
Example: In the following figure, insertion points (1) and element points (2) are both shown.
If the Object snap option is activated, then these points are used as snap points. Graphical objects are then automatically joined at these points on insertion.
In addition to the element points, other points are used as handles:
- Middle points of lines and polyline segments
- Middle points of circles, arcs, and ellipses
- Intersection points of elements.
Perpendicular and tangent points
If the Object snap option is activated when drawing graphical elements, a perpendicular or tangent point is displayed at the cursor as soon as a perpendicular 
or tangent 
line element is possible.
If the Object snap option is deactivated then this (and other) points are not treated as corner handles and are accordingly also not displayed.
Perpendicular or tangential mode when drawing
Irrespective of whether the Object snap option is selected, the two modes Perpendicular and Tangential are available in the popup menu when drawing particular graphical elements (lines, circles etc.).
These functionalities can help you draw a perpendicular line or a tangent. Once you have selected a mode in the popup menu, the icon on the cursor changes. The respective modes for the following graphical elements are then available:
- Perpendicular mode (Cursor:
): for lines, polylines and polygons - Tangential mode (Cursor:
): for lines, polylines, polygons, circles, arcs through center and sectors.
See also