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Warning: The behavior of snap modes is slightly unusual when you are moving an object using OLE drag and drop. It is therefore not a recommended method for moving objects that require precise placement.
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Nudge
If you pick up an object by the reference point you can nudge its position using the numeric keypad. The NumLock key must be on for this to work.
Pick the object up by its reference point. Use 4 and 6 to move the object along the X Axis, use 8 and 2 to move the object along the Y Axis. Each time you tap a key the object will move a small amount in the associated direction. Holding down the Shift key will cause the distance moved to be significantly greater.