Object snaps

The object snaps constrain the marker to an exact location on an object such as the end of a line or the center of a circle.

Steps:

On the status bar, click Osnap.
Select or clear the desired object snap check boxes.

Simple object snaps

End End
Snap to the end of a curve, text corners, interior vertices of polylines and joined curves, the seam point on closed curves, and the "corners" of surfaces, and polysurfaces.

Near Near
Snap onto a curve, mesh wire, surface edge or SubD edge at the cursor location.

Point Point
Snap to a point object, extrusion point, control point, edit point, block, and text insertion points.
Also snaps to centers and corners of rectangular lights and block insertion points even if control points are not displayed.

Midpoint (Mid)
Snap to the midpoint of a curve, surface edge, mesh wire, polycurve segment, SubD edge or adjacent smart points.

Center Center (Cen)
Snaps to the center of:

Intersection (Int)
Snap to the intersections of curves, edges, mesh wires, and isoparametric curves on a surface.

Percpendicular Perpendicular (Perp)
Snap perpendicular to a curve, mesh wire, or surface edge.

Tangent Tangent (Tan)
Snap tangent to a curve.
The Tan object snap is not effective for the first point for a command.

Quadrant (Quad)
Snap to the point on a curve that is at the maximum x or y point relative to the current construction plane.

Knot Knot
Snap to a knot on a curve or surface.

Knot Vertex
Snap to a mesh vertex.

Project

The ProjectOsnap command projects object snaps from the actual snap point to the construction plane.

Disable

The DisableOsnap command manages the state of persistent object snaps.

To temporarily turn off persistent object snaps, check the Disable checkbox in the Osnap control. This will temporarily suspend persistent object snaps.
Uncheck the "Disable" checkbox to reactivate all persistent object snaps.
To clear all persistent object snaps, right-click the Disable button in the Osnap control.