All dog leashes serve the same basic purpose -- to keep your dog under control while out and about. For general walking and training applications, any leash works about as well as any other. If your dog has specific problem behaviors, or if you are trying to teach specific lessons, match the style of leash to your chosen application.
Standard leashes are made of nylon or leather. Nylon is strong, flexible and durable, and stands up well to harsh conditions. It is lightweight enough to be appropriate for a small puppy but heavy-duty enough to restrain even large dogs. However, nylon leashes can cause abrasions if the dog pulls the leash out of your hands. Leather leashes are tough and can take a great deal of abuse. They soften as they age, conforming to the body. They are sometimes expensive but typically do not need to be replaced throughout the dog’s life. Leashes are also available in other materials such as cotton and even rubber, but these are typically novelty products that do not hold up well over time.
Also known as a flexi-leash, the retractable leash allows variable leash length. Like a tape measure, the leash pulls out from a heavy handle with a stopping mechanism that you control. Although such leashes are easy to store and use, "Consumer Reports" and The Dogington Post noted several potential problems. If you do not tightly set the stopping mechanism or leave it loose to give your dog freedom, you are at risk of cuts and abrasions if the dog suddenly lunges forward causing the leash to rapidly unravel from the base. Even with the mechanism set, your dog could pull the entire handle out of your hands, injuring himself, you or a bystander in the process. Likewise, the dog is at risk for strangulation when he suddenly runs out of leash or if he becomes entangled in the leash. Choose a retractable leash only when walking a dog that responds well to voice commands and in situations that are not likely to cause the dog to bolt.
Chain leashes are heavy, bulky and uncomfortable in the hands. They are most often used with training collars but may be attached to any solidly constructed collar. A chain leash is useful for dogs who bite or chew their leashes, as the metal causes discomfort in dogs' mouths. Chain leashes with leather handles are much more comfortable for the handler.
A Martingale lead is an all-in-one product that includes a Martingale collar and a standard leash. Unlike a traditional buckle collar, the Martingale collar tightens when the dog pulls against it and releases when he stops pulling. A properly fitted Martingale collar never puts the dog in danger of choking but maintains just enough pressure to be uncomfortable when the dog pulls. Martingale collars are most often used when training specific behaviors such as those performed by show dogs.
A standard walking leash is typically 6 feet long, although owners with small dogs and those who live in crowded cities sometimes prefer 4-foot leashes. These lengths give a dog enough slack to comfortably explore his surroundings but are short enough to prevent the dog or handler from getting tangled in the leash. When you are training commands, such as the "Stay," that require you to be further away from the dog, an 8-foot training leash is best. This length allows you to maintain control while giving the dog enough slack to follow the voice command. For specialized applications such as tracking, very long leashes, up to 150 feet, are available. Very short leashes, often called handle leashes, are just 1 to 2 feet in length. They are primarily used to train show dogs in very specific walking and heeling behaviors.