A really famous and found useful tool to lots of superheros who dont posses any super-human powers.
Rorschach posses this gadget, which he can carry with him in his trench coat. We see him use in two occasions, when he climbs up to Edward Blake's Apartment, to investigate Edward Blake`s death in Chapter I (see also Chapter I: At Midnight, All the Agents... , and in Chapter V (see also Chapter V: Fearful Symmetry when he shoots a cop only to inhabilitate him so he could escape.
While the gadget known as grappling hook ( and grappling hook gun's) do exist, in comic books they have an additional fantastic properties, such as the ability to reach extremely high or long distances, a extremely resistant rope and hook that can lift people, an unusual long rope (usually compared to the size of the gun) and sometimes even to pull things towards the gun instead of doing the opposite; a good example of this could be Batman.
Despite that fact Alan Moore, trying to give some sort of realistic sensation to his novel, shows Rorschach grappling hook more as a normal hook than one we would expect in a superhero comic book, its a gas powered hook gun which he uses to climb up to Edward Blake's apartment, shooting the hook up and climbing up the rope, instead of the gun lifting him up to the apartment, and once to shoot a cop. The only things that can be said to be abnormal about the hook is the fact that Rorschach carries it in his trench coat and the rope is still long enough to reach a 20th floor of a building (and some people might also question the fact that he shoots someone with the hook only, while the rope doesn't moves at all).
While in the comic Moore decides that the hook wont lift Rorschach right up to Blake's apartment, in the film they stick to the "traditional" super hero grappling hook guns, and make it lift him.