I'm afraid I would have to respectfully disagree with your teacher in this point...
Gerunds, in common with many nouns, can be used attributively (i.e. as modifiers). Where a preposed -ing form denotes the purpose of something (i.e. as opposed to an action that it is performing), we customarily classify it as a gerund.
Thus 'fishing rod' means 'rod for fishing', not (absurd) '?rod which is fishing' and would therefore also be termed an attributive gerund.
You may also be interested to note that there is a clear phonetic difference regarding [Ving + N] phrases corresponding to the syntactic distinction: where Ving is a gerund, it takes the phrase stress (thus 'FISHing rod', not 'fishing ROD'), whereas, when it is a participle, the stress falls on the noun (e.g. 'sitting DUCK', not 'SITTing duck').
I trust that fully answers your query!