on tenterhooks, to be

In a state of painful suspense. The frame on which newly woven cloth was stretched was called a tenter and the hooks used to hold the cloth in place thus were tenterhooks. Tobias Smollett appears to have been the first to use the term metaphorically: “I left him upon the tenterhooks of impatient uncertainty” (The Adventures of Roderick Random, 1748). Clothmaking has changed, and “tenterhook” today survives only in the cliché.