Used attributively to describe tools, stones, etc., related to the act or purpose of sharpening.
Used as an attributive noun to modify another noun (e.g., "sharpening kit")
sharpeningгерундий или причастие настоящего времени Used attributively: e.g., "a sharpening stone"
sharpenгерундий или причастие настоящего времени ‘sharpening’ is used attributively (e.g., “a sharpening stone”) and thus functions as an adjective.