Use the adverb alongside when two things are right next to each other, like a boat and a dock or a hunter and her loyal dog.
If you pull up alongside your friend's car in a parking lot, it means that you've parked directly beside it. Alongside can also imply cooperation, as when a baker's assistant works alongside him, kneading dough and wiping flour off the counter. Alongside was once a phrase, either "along side" or "along the side," both primarily used in a nautical sense, to talk about boats. In the 1700s it became a single word.