Couplers provide the perfect solution for the person wanting to walk two dogs at the same time.
Things to consider:
Breed Considerations - Most people these days have more than one pet, but it may be difficult to walk them at one time -- particularly if they are different breeds. An adjustable coupler makes it easier to take your Doberman and your Shih Tzu for a stroll than if you were relying on a separate lease for each.
Freedom- Everyone's pets get along less than spectacularly from time to time. Whether it's sibling rivalry, territorial issues, or just a bad day, you can still take your pets for a walk. With the right coupler, your pets can have the joy and freedom of a walk, while still maintaining a nice distance between them. This is also wonderful if you have one dog who likes to bound ahead while the other prefers to simply mosey along.
Good Dog, Bad Dog - When using couplers to walk two dogs at once, hook the lead and coupler to the collar of your feistier dog. Putting the leash on the dog who pulls, tugs, or gets easily distracted will give you more control over him, while not putting too much stress on your other pet. Your more excitable dog will feel any corrections more directly than the more obedient dog.