顺手 (shùn shǒu) means 'handy' as an adjective (e.g., a tool that feels natural to use) and 'while you're at it' as an adverb (doing a small extra task without extra effort). As an adverb, it's similar to 顺便 (shùn biàn) but more physical — 顺手 implies using your hands in the same motion, while 顺便 is broader (any errand). As an adjective, it's distinct from 方便 (fāng biàn), which means 'convenient' in a general sense (location, time, ease).