"But, even after so long we could only make a nail. Chaa, how'd you make the
gun?"
"Form all the separate parts and then assemble them."
"The one just now was also a part?"
“Mmm. It’s the firing pin's core.”
“That means…… You remember perfectly the structure of a gun?”
“Yes.”

- Angel Beats! Track Zero, Chapter 5, Page 7