Width: Specify a valid
for the working plane raster. This raster is used only for displaying
the drawing plane and has no effect on mouse input.
Auto: This check button activates or
deactivates the automatic raster width adjustment mode. When in auto mode,
the raster size is automatically adjusted if the working plane is rather
large according to the current raster size.
Snap: This check button activates or
deactivates the snap mode. When the snap mode is active, all mouse cursor
locations in the drawing plane are mapped to the fixed Snap
width raster.
Snap width: Specify a valid
for the raster snap width. This raster is not used for displaying the
drawing plane but for mapping mouse pointer locations to a fixed raster.
The default raster is 0.1 units. All mouse pointer locations which are
projected onto the drawing plane during the interactive shape generation
process are then mapped to the fixed snap raster
Auto: If
the auto button for the snapping is enabled, on change of the raster size,
the snap width is checked and if not within a valid range compared to
the raster will be adjusted.
淘宝官方店 
Working Plane
