Here mine dog "Flame" has her confront made perfectly symmetrical through a bitof picture magic.
The white line down the center is theline of Symmetry
When the folded component sits perfect on top (all edges matching), then the fold line is a heat of Symmetry.
Here I have actually folded a rectangle one way, and it didn"t work.
But as soon as I shot it this way, that does work (the folded component sits perfect on top, every edges matching):
Triangles
A Triangle can have 3, or 1 or no lines of symmetry:
 |  | |||
| Equilateral Triangle(all political parties equal, all angle equal) | Isosceles Triangle(two political parties equal, 2 angles equal) | Scalene Triangle(no sides equal, no angles equal) | ||
| 3 currently of Symmetry | 1 heat of Symmetry | No lines of Symmetry |
Quadrilaterals
Different varieties of square (a 4-sided airplane shape):
 |  | |||
| Square(all political parties equal, all angles 90°) | Rectangle(opposite sides equal, all angle 90°) | Irregular Quadrilateral | ||
| 4 currently of Symmetry | 2 lines of Symmetry | No present of Symmetry |
 |  | |
| Kite | Rhombus(all sides equal length) | |
| 1 line of Symmetry | 2 currently of Symmetry |
Regular Polygons
A consistent polygon has actually all political parties equal, and also all angle equal:
| An Equilateral Triangle (3 sides) has 3 present of Symmetry | ||
| A Square (4 sides) has 4 lines of Symmetry | ||
 | A Regular Pentagon (5 sides) has 5 lines of Symmetry | |
 | A Regular Hexagon (6 sides) has 6 present of Symmetry | |
 | A Regular Heptagon (7 sides) has 7 present of Symmetry | |
 | A Regular Octagon (8 sides) has 8 lines of Symmetry |
And the sample continues:
A regular polygon the 9 sides has 9 lines of SymmetryA constant polygon the 10 sides has 10 currently of Symmetry...A continuous polygon that "n" sides has "n" currently of SymmetryCircle |