Howto draw a empty rectangle in opengl?

Need draw a hollow rectangle in opengl and i try this using primitive objects:

void Skin::draw()
{
    glColor4f(1.0, 1.0, 1.0, 1.0);
    glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);

    glBegin(GL_POLYGON);

    glVertex3f(-0.8, -0.86, 0); // XYZ left, top
    glVertex3f(-0.7, -0.86, 0); // XYZ right, top
    glVertex3f(-0.7, -0.96, 0); // XYZ right, bottom
    glVertex3f(-0.8, -0.96, 0); // XYZ left, bottom
    glVertex3f(-0.8,  -0.86, 0); // XYZ left, top (close)

    glVertex3f(-0.79, -0.87, 0); // XYZ left, top (diagonal down-right)
    glVertex3f(-0.79, -0.95, 0); // XYZ left, bottom
    glVertex3f(-0.71, -0.95, 0); // XYZ right, bottom
    glVertex3f(-0.71, -0.87, 0); // XYZ right, top
    glVertex3f(-0.79, -0.87, 0); // XYZ left, top (close)

    glVertex3f(-0.8, -0.86, 0); // XYZ left, top (close diagonal top-left)

    glEnd();
}

Bug the result is a fill rectangle :(