The Snaps and Constraints allow you to control how you draw and move objects. Using the different settings will allow you to draw straight lines and rotate objects evenly. Left clicking on the check box will activate each of the controls. You may choose an Angle Snap setting by clicking on the radio button.
Point: This will allow you to snap to all of the points on any shape in your project.
Line: This will allow you to snap to any edge of any shape in your project.
Grid: As you draw a shape, your lines and arcs will snap to the grid. This also affects the movement of shapes or objects as well.
Centerpoint: This will snap to the centerpoint of any arc in your scene, where each radius line starts.
Perpendicular: Using this option, you can move an individual line or arc perpendicular to itself.
Midpoint: This will snap to the midpoint of any line or arc in your scene as you draw.
Auto Adjust Arcs: This option will change the results you see while using the move or scale tools to adjust an existing arc. While on, the move and scale tools will attempt to maintain a proper freeform shape. When off, moving arcs will draw a line.
None: This option will turn off angle snapping, which affects drawing shapes or rotating objects and shapes in your project.
Relative Angle: With this option, as you draw a shape, lines and arcs will snap 45 degrees relative to the previous line or arc drawn.
World Angle: With this option, as you draw a shape or rotate an object, it will snap to every 45 degrees globally.