Maya places vertices on the ground plane unless
you snap them to existing geometry.
Click
to place the next vertex. Maya creates an edge between the first point
and the last point you placed.
Place
another vertex. A dashed edge connects the three vertices.
Do
any of the following:
Press to finish
the polygon.
Press to delete
the last point you placed.
Press
y to start a new polygon.
Continue
placing vertices to create a quad or n-sided polygon.
To
switch to editing vertices, press Home or Insert. A manipulator
appears on the previous vertex. Use the manipulator to move the
vertex, press Delete to delete a segment, or click another vertex
to edit it. Press Home or Insert again to finish.