Swage

"I made a swage and hammered out the test bars to the required .615 inch plus or minus .003, the thickness of a sheet of paper. […]

If he were making round or square-sectioned nails, the blacksmith also kept a "swage" near the anvil. If different sizes, shapes, and heads were required, the nailor had a number of swages or a number of holes in the one swage.

[…] The blacksmith let me help out, hold the horse while he was putting the shoe on, turn the hand forge, clean up the shop. And after awhile he taught me names of everything. He'd say, 'Boy, hand me the three-inch swage,' and I had to know just what he wanted. I learned that way."

apt words have power to swage