Keyboard SNAP or F9
Snap mode takes AutoCAD one step further than the drawing board. With Snap mode turned on AutoCAD only allows you to pick points which lie on a regular grid. The Snap grid is completely independent of the display grid. However, the Grid spacing and Snap spacing are usually set to the same value to avoid confusion. You can force the display grid to conform with the snap grid by setting the display grid spacing to zero. The display grid will then automatically change each time the snap grid is changed. When Snap mode is turned on and the Grid is displayed, the Snap and Grid spacings are the same and the crosshairs will jump from one grid point to another as you move across the screen. This makes it very easy to draw objects which have a regular shape. The Snap command is used to set the snap spacing and to toggle Snap mode.
Specify snap spacing or [ON/OFF/Aspect/Rotate/Style/Type] <10.0000>: (enter the required snap spacing in drawing units)
Although you can use the Snap command to turn Snap mode on and off, it is much more efficient to use the F9 function key on the keyboard or to click the SNAP button on the status bar.
The "Aspect" option can be used to vary the horizontal and vertical snap spacings independently.
"Rotate" is used to set the snap grid to any angle.
You can also set the snap style to either Isometric or Standard (the default) using the "Style" option. The Standard style is used for almost all drawing situations including detail drawings in Orthographic Projection. The Isometric style is specifically to aid the creation of drawings in Isometric Projection (see the illustrations on the right).
The "Type" option allows you to set the snap type to either Grid (the default) or to Polar. The Polar option can be used in conjunction with Polar Tracking so that Snap mode snaps along polar tracking angles rather than to the grid.
The grid snap is particularly useful if you need lots of modular objects such as bricks or paviors. In the illustration on the left, the Aspect option is used to set the X and Y snap spacings to the brick dimensions and the Rotate option is used to set the orientation of the bond. Once these settings are made, the bricks can be accurately drawn without any other drawing aids.
All of the Snap variables can also be set using the Drafting Settings dialogue box. Right-click on the SNAP button and choose Settings… from the menu.