Walaikumussalam
Rule 257. It is not necessary that the wiping of the head should be performed on its skin. It is also in order if a man wipes the hair on the front of his head. However, if the hair are so long that when combed they fall on his face, or on other parts of his head, he should wipe his hand on the roots of his hair, or part the hair and wipe the skin. If a person collects his hair on the front side of his head, or on other parts of his head and wipes them, or if he wipes the hair of other places, such a wiping w ould be void.
Wassalam