Rule 7 warns us for words having כ at their head.
If כ is the particle meaning as, like, then we should find נוהג in our dictionary. Now, maybe you'll find it and maybe not.
How is this possible? In a general way this word has its entry in dictionaries as נֹהַג, custom, practice.
Only few have נוֹהַג or נוהג.
Look at ptr N-t129.
Meaning: as custom, like practice.