This is my take on the grappling hook that Luke Skywalker used to swing Leia across the Death Star chasm in A New Hope. It's by no means screen accurate. I've seen loads of different takes on this prop and lots of different images and varying models of it in different books and online, so I've taken my favourite parts and made a Frankenstein one for myself.
The body of the box is cut and bent from the case of an old PC and backed onto a sheet of ABS plastic that was leftover from building my Stormtrooper armour. The hook has aluminium legs that are cut from old door handles and they are hinged on the body of an old mini tripod. The central sprung column is a length of half inch all thread covered in black heat-shrink, cobbled together from various odds and ends from the workshop.
The retractable string comes from a key fob from officeworks and I threw in some LED's for good measure. The whole unit fits onto my Stormtrooper utility belt incase I come across anything massive that needs scaling.