en_tn/isa/41/05.md

Yahweh continues speaking.

The isles

You can translate "isles" the same way you did "coastlands" in Isaiah 41:1.

anvil

an iron block on which a person shapes metal with a hammer

They fasten it with nails so it will not topple over.

Here "it" refers to the idol which they are repairing because they think it will protect them from Yahweh.