The clicker is a small hand-held device that makes a distinct, short sound to mark a desired behavior. (See clicker training for a more detailed discussion of this methodology.) It has gained popularity in recent years as being a means of training that does not involve physically correcting the dog, though it may be used in conjunction with these methods.
Prong collars must never be turned inside out (with the prongs facing away from the dog's skin), as this may cause injury against the body and head.  Plastic tips are occasionally placed on the ends of the prongs to protect against tufts forming in the fur or, in the case of low quality manufactured collars with rough chisel cut ends, puncturing the skin. Like the slip collar, the prong collar is placed high on the dog's neck, just behind the ears, at the most sensitive point.