To Turn On Grid Snap and Set the Snap Spacing

1. Click Tools menu Drafting Settings.
2. In the Drafting Settings dialog box, Snap and Grid tab, click Snap On.
3. Under Snap Type, make sure Grid Snap and Rectangular Snap are selected.
4. In the Snap X Spacing box, enter the horizontal snap spacing value in units.
5. To use the same vertical snap spacing, press Enter. Otherwise, enter a new distance in the Snap Y Spacing box.

Note:

Grid snap can be turned on and off with several other controls, including the F9 key and the Snap Mode button on the status bar. ( Find)

You can suppress snap temporarily by holding down F9 while you create or modify an object.