Perpendicular snap

Use the Perpendicular snap to snap to a point perpendicular to the selected entity. You can snap to an arc, circle, ellipse, line, polyline, infinite line, ray, spline, hatch pattern, or edge of a plane to form a perpendicular alignment with that entity or with an imaginary extension of that entity.    

To set the Perpendicular snap    

Do one of the following to choose Perpendicular ():

    On the ribbon, choose Draw > Perpendicular (in Entity Snaps).

    On the menu, choose Tools > Entity Snaps > Perpendicular.

    On the Entity Snaps toolbar, click the Perpendicular tool.

    Type perpendicular and then press Enter.