one of our three concrete jockey's

The writer of this Hastings Racecourse advertisement in today's 24H Vancouver thinks that an apostrophe is need when creating a plural form of a noun. In fact, the word jockeys above should not have an apostrophe. Put an apostrophe in jockeys only if writing about something a specific jockey owns. For example: the jockey's underwear. Click the image to enlarge it.