Offset
Dialog Box

Offsets selected faces by a specified distance.
Offset DistancePositive values create an offset in the face normal direction; negative values create an offset in the opposite direction.
Duplicate and offset
If this toggle is on, it creates new faces for the offset. Otherwise the selected faces itself gets offset.
- Move boundary along neighbor faces
If this toggle is on, faces adjacent to the selected faces act as guides for the sides. Otherwise it moves along the face normal.
Example 1
In this example the selected face is offset for a negative distance with duplicate option.
Input

Move boundary along neighbor faces - OFF

Move boundary along neighbor faces - ON

Example 2
In this example the selected face is offset without duplicate option.
Input

Offset for a negative distance.

Offset for a positive distance.
