When using the Move Tool and various creation tools, you can snap to existing objects in the scene.
To snap a move, press 
on the object you want to snap to (pressing 
just selects the object).
| To snap to... | Hold | Or turn on this icon in the Status Line (toolbar) |
|---|---|---|
| Grid intersections |
x |
 |
| Curves |
c |
 |
| CV, vertex, or pivot |
v |
 |
| View plane |
 |
If you have snapping turned on and drag an arrow on the position manipulator (as opposed to the center), the manipulator snaps to the first available point along that axis.