Marius, true keris pijit are in fact made from material that is about as thick as a piece of paper. 
 
The hot iron that I put dents into was also paper thin.  
 
I guess that thicker material could also be indented in the same way, if one were sufficiently strong and sufficiently fast and one's skin was sufficiently thick and toughened.
		 
		
		
		
		
		
		
		
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