Charles Ellicott Commentary Isaiah 41:7

"So the carpenter encourageth the goldsmith, [and] he that smootheth with the hammer him that smiteth the anvil, saying of the soldering, It is good; and he fasteneth it with nails, that is should not be moved." — Isaiah 41:7 (ASV)

So the carpenter. —The process is described even more vividly than in Isaiah 40:19. For “the carpenter,” read the caster, the idol being a metal one. The image of lead or copper is then covered with gold plates, which are laid on the anvil, and are smoothed with the hammer; the soldering is approved by the artist, and then (supreme touch of irony) the guardian deity is fixed with nails, that it may not totter and fall.