Status bar > Grid and Snap panel > 2D Snap, 2.5D Snap, or 3D Snap on the Snaps flyout
The buttons on this flyout provide control over the range of 3D space where snaps are active.
Snaps flyout
Object snapping lets you snap to specific portions of existing geometry during creation and transforms of objects or sub-objects. You can also snap to the grid, and you can snap to tangents, midpoints, pivot points, face centers and other options.
The mode you choose maintains its state when you switch levels.
When snapping is on (but Animate is off), rotations and scales are performed about the snap point. For example, if you're using Vertex snapping and rotating a box, you can rotate it about any of its corner vertices.
When the Animate button is on and either Select And Rotate or Select And Scale is selected, the Snap Toggle button is disabled, and rotation and scaling is performed about the pivot point of the object.
The mouse snaps absolutely to the active snap types. Relative snapping is also available. As a default, when you turn on the Snap Toggle button, only the Grid Points snap type is active. If you perform a Move operation, the cursor will snap to the grid, but you can select and pick up an object that's not aligned to the grid. When you move the object and snap it to grid points, the object's original position relative to the grid is maintained as an offset to each grid point, providing relative snapping.
To move the same object in an absolute fashion, add the Vertex snap type. Then, when you select the object to move, you select one of its vertices, and snap that vertex to any grid point, resulting in an absolute snap.
You can also achieve variations on relative snaps by turning on the Selection Lock Toggle button in the status line.
A wide variety of snap types are available from the Snaps dialog that you use to activate different snap types as you work.
See also
Procedures
To turn snap on an off during a transform:
Press S to toggle snap off when it gets in the way.
To use snaps to move a relative distance:
Turn on Snaps with the S key, or by clicking the Snaps toggle.
Lock your selection set with the SPACEBAR, or by clicking Lock Selection on the status bar.
Wherever you click in the viewport, the snap will stay relative to the distance of your cursor to the object.
To use snaps to move an absolute distance:
Turn on Snaps with the S key or by clicking the Snaps toggle.
Click the selection. Snap uses the point you click for the snap source.
Move to whatever target snap you desire. The object will snap to an absolute distance.
Interface
This flyout button provides three modes:
2D Snap: The cursor snaps only to the active construction grid, including any geometry on the plane of that grid. The Z axis, or vertical dimension, is ignored.
2.5D Snap: The cursor snaps only to the vertices or edges of the projection of an object onto the active grid.
Suppose you create a grid object and make it active. You then position the grid object so you can see through the grid to a cube further off in 3D space. Now, with 2.5D set, you can snap a line from vertex to vertex on the distant cube, but the line is drawn on the active grid. The effect is like holding up a sheet of glass and drawing the outline of a distant object on it.
3D Snap: This is the default. The cursor snaps directly to any geometry in 3D space. 3D snapping lets you create and move geometry in all dimensions, ignoring the construction plane.
Right-click this button to display the Grid and Snap Settings , which lets you change snap categories and set other options.