rake thin

What is the meaning of rake in the following sentence :
She had ordered firewood from an old man and his grandson, both rake thin and surprisingly strong, who would turn up and throw logs to each other as if they were fruit.

Is rake a verb in this sentence ? An adjective ?

Would you say that ' he is rake think' to mean he is think like a rake. I am just guessing.

ta

The word in your quoted text is thin, not "think".

"rake thin" is the same as "as thin as a rake"

From the Oxford Dictionaries:
(as) thin as a rake (of a person) very thin

You'll find this definition in many online dictionaries.

You may also see "rail" instead of "rake"; the meaning is the same.

Also 'stick thin'.