Circumcision was Performed with Knives of Flint
Source: TTT
Exodus 4:25
But Zipporah took a flint knife, cut off her son’s foreskin, and touched it to Moses’ feet. “Surely you are a bridegroom of blood to me,” she said.
Joshua 5:3
So Joshua made flint knives and circumcised the sons of Israel at Gibeath-haaraloth.