Trying to draw a diamond shape from a shape - Please help !!!

Question

Hi,
I am trying to draw a diamond shape from a custom shapes library but having a hard time getting it to shape accurately, the shape I am trying to draw should look like this :
If someone can teach me some photoshop techniques as to how to get all the angles reshaped accurately using some photoshop tools that will be great or if you can do it in my project file that will help too, the project psd file can be downloaded from here : http://tonyalepski.heliohost.org/Diamond.psd
Your help would be really really appreciated.
Thank you very much !!
Tonya.

Answer 1

Your diamond looked like it was square to me. So I centered your diamond over your canvas add a vertical  guide at 50%. Measured your square to be 190 PX  Dragged out a 190 PX square shape no fill 1 px red stroke.  Transformed the shape rotating it 45 degrees and moved it up to align with your diamond.   Dragged out a horizontal guide to match your diamond cut. Used the Pen tool to add two control points the square shape. and then use the pen tool to delete the top control point then convert control point tool to convert the two added control points.
http://www.mouseprints.net/old/dpr/Diamond.psd