管中窥豹，可见一斑guǎn zhōng kuī bào , kě jiàn yī bān

look at one spot on a leopard and you can visualize the whole animal—conjure up the whole thing through seeing a part of it
❍ ～，与他打一次交道，你就能判断他的人品。If you look at one spot on a leopard,you can visualize the whole animal; if you have dealings with him just once,you can judge his character.