Here is a short video of a tool I made for registering punch marks on two sides of a piece of stock for punching.  It works well on square, round, and flat stock.

 

The dies are made of H13 so you can mark on both hot and cold stock.  The bottom die is a strike line so you can see it on hot metal.  When you turn the stock over, you line up the punch in the strike and you end up with a punch mark on both sides.  The punch on the top was made by brazing the H13 to a piece of cold rolled 1/2 inch so it would work with the bronze bushing in the guide.

 

http://www.youtube.com/watch?v=q5w3QsH3m3k

Why did you make a strike line die? Why not 2 punches and mark both sides in one operation? What do I not understand?

What is a strike line die? How is it diff than a center punch?

 

Cool tool.

I have a punch die for the bottom, that is what I started with.  But I can't see the mark well on the hot glowing steel.  I can see the line and locate the punch mark with no trouble.