一把钥匙开一把锁

yī bǎ yào shi kāi yī bǎ suǒ

One key opens one lock.

There is a different solution for each problem. (idiom)

one

to hold; to grasp

yào

key

shi

used in 鑰匙|钥匙[yao4 shi5]

kāi

to open (transitive or intransitive)

one

to hold; to grasp

suǒ

to lock; to lock up