Question: Am I correct that when Henry Fonda is questioning the E.G. Marshall character about his recent activities Marshall says that the night before he worked until 8:30 then went home? The trial was every day for the past several days.
Question: Did they ever look at the hole in his pocket that the knife supposedly slipped out of?
Answer: If you're referring to the jurors, no. We see the entirety of their deliberations. If you're referring to the prosecution or defense, that is unknown. Given, however, that none of the jurors brought up the question, it's likely there was at least a check of his clothes to verify he had a hole in his pocket.
Given how easy it would be to simply tear a hole as an excuse, even if it was there, it wouldn't be much in the way of corroboration.
Answer: He was actually talking about the night before the last one. Trials, especially longer ones for serious crimes such as murder, are not usually on consecutive days...often there is a recess after the prosecution rests, and another after the defense, before closing arguments and the jury's deliberation. During those recesses, unless they are sequestered, the jury members would return to their normal lives (including work), and report back to the court when summoned.