Command entry: Shift+right-click a viewport. 
Snaps shortcut (quad) menu Snap Options quadrant Grid and Snap Settings
This command displays the Grid and Snap Settings dialog. This modeless dialog establishes settings and options for snaps, the home grid, and user-defined grids.
Controls on the Grid And Snap Settings dialog determine which snap settings are used when you activate snaps by clicking 3D Snap Toggle. Adjusting any of these snap settings does not automatically turn on snaps.
You can use objects within an XRef scene as snap references.
To change grid and snap settings:
Grids And Snaps Grid And Snap Settings and click the appropriate tab.
Snapping gives you additional control when creating, moving, rotating, and scaling objects by causing the cursor to “jump” to specific portions of existing geometry and other scene elements during creation and transformation of objects or sub-objects. The controls in this dialog set the snap strength and other characteristics such as the snap target.
Snap Override lets you supersede all the currently selected snap types and temporarily use only one, or none, of the snap types currently selected on the Grid And Snap Settings dialog. For example, you might be creating a spline while snapping to grid points, but then need to snap one of its vertices to the midpoint of an object.
The Options panel of the Grid And Snap Settings dialog lets you set options related to snapping.
The Home Grid panel of the Grid And Snap Settings dialog sets the spacing and other characteristics of the home grid. Choosing useful home grid settings can simplify the construction process. The home grid provides a visual reference for creating objects in a scene.
The User Grids panel controls automatic activation of grid objects and settings for AutoGrid.
