Mr. Eisenberg. And in working with these tools, as I understand your testimony, you have found that the markings which a tool leaves, which the same tool leaves, will be distinctive.
Mr. Frazier. That is true, yes. When it is a scrape or an impression from its surface, or something of that nature, it can be very readily identified. But if it is a drill or something of that nature, where you have a tearing operation, then it is not readily identified, but it occasionally can be identified.
Mr. Eisenberg. Well, how many such examinations do you think you have made?
Mr. Frazier. Thousands of them.
Mr. Eisenberg. Have you noticed whether the marks left by a given tool—that you have examined—change over the course of the use of the tool?
Mr. Frazier. Yes, they change very rapidly when a tool is used to cut a hard object.
Mr. Eisenberg. Could you elaborate on what you mean by "very rapidly"?
Mr. Frazier. Well, for instance, when using a pry bar, for example, one insertion of a pry bar into the hard insulation of a safe, with pressure applied to it can change the entire blade of the tool to the extent that you could not identify a succession of marks, because of the abrasion by the insulation. But that same tool, used to mark a soft steel or brass or copper, could make mark after mark without changing, or only a small portion of it may change with each impression. Or it may gradually change over a period of time.
Mr. Eisenberg. Now, is the metal in the bolt face a hard metal or a soft metal?
Mr. Frazier. I would say it was hard metal——