lathe, lath

Lathe or lathe means a machine used to cut and shape wood or metal while turning it --
He wants a lathe for his woodworking shop.
I can used the lathe to make a new leg for the chair.

Lath or lath means a thin strip of wood, most commonly used to hold plaster or roof slates --
Do you know how to repair an old lath and plaster wall?
You'll need a lath to hold the slates in place.

Now that you know that, you can say --
"The wall is lath and plaster, but the posts were turned on a lathe."