As shown in the figure, it may be a parallelogram or an irregular quadrilateral.

If you want to make a rectangle, all four internal angles are right angles, then this triangle must be a right triangle, and only when the hypotenuses are put together can you form a parallelogram.

If you want to spell a diamond, the four sides of the diamond are equal in length, then it should be at least an isosceles triangle with the bottom sides spliced.

If you want to make a square, it must be an isosceles right triangle with hypotenuse together.

12 is a diamond,

Prove:

Triangle AOH is the same as triangle COF, so AH=CF, so DH=BF,

Similarly, DG=BE, CG=AE,

So the triangle AHE is congruent with the triangle CFG,

So, he =GF,

Similarly, HG=EF,

So the triangle HGE is congruent with the triangle FEG,

So the angle HGE= the angle FEG, so HG is parallel to EF, so the quadrilateral EFGH is a parallelogram.

As can be seen from the meaning of the question, its diagonal is vertical, so it is a diamond.