When Jewell was being touted as the likely bomber, some of the evidence they cited was that he had nails in his basement that were of the same type used in the bomb.
They were the same type of nail that just about anybody with a basement has in their basement. Metal ones, with a point on one end, and a flat part to hit with the hammer on the other end.
Actually, dead, I read that the nails in Jewell's basement were made from metal or a metal-related substance - which is precisely the material that the nails in the bomb were made from.