"pins & needles"?

[Bethany K. Dumas]

On Thu, 10 Oct 2002, sagehen wrote:

> The evidence on "pins & needles" seems pretty conclusive and, hell, now
>that I've had half a day to think about it, I realize that I've probably
>used it in just this way myself.  "Tenterhooks" still seems more natural to
>me, but clearly that has faded out of common parlance.  Tenterhooks, by the
>way, are little hooks ranged along the side of a framework, as in a curtain
>stretcher, to hold material taut.

Thanks. Now - What is a curtain stretcher? What is it used for? Why would
one want to stretch a curtain?

Bethany