下手 (xià shǒu) means 'to set about / start doing' and focuses on the first physical or practical action of a task — it's used when you're about to actually do something with your hands or begin a concrete process. It's more specific than 开始 (general 'begin') and overlaps with 动手 (also 'start working on'), but 下手 often implies a careful or deliberate first move, while 动手 can also mean 'to hit' or 'to touch'.