Grapple Guns are hi-tech pistols that fire small grappling hooks on monofilament wire. Once the hook is secure, a button press will activate a powerful motorized pulley system that will allow the user to make a quick ascent to a rooftop. Variations of this gadget ares used constantly by Batman and the rest of the Batman Family.
It can also be used offensively to pull people or objects. Sometimes this requires a different attachment, like the Bat-Claw.
Early versions of this gadget, such as the Batpoon or harpoon gun rifles featured no motorized pulley system, Batman had to physically climb the rope once fired. Batman rarely used such devices, typically justing using a Batarang as a hand thrown grappling hook.