I'm not sure what the costume was, but a buddy of mine needed a grappling hook for a cosplay, so I came up with this.

Print the parts in the quantities listed below.  You may need to drill or ream the dowel holes to 3mm if you use actual steel dowel pins.  If you print the supplied pins you can just hammer them in with a small jewelers hammer.

Quantities:

• 1x Body A
• 1x Body B
• 1x Coil
• 3x Tine A
• 3x Tine B
• Optional:
  • 14x M3x12  (alternatively, you could use M3x12 dowel pins instead of printing these

Assembly:

• Main Body:
  • Lightly tap two M3x12 dowel pins into Body A.
  • Apply glue of choice to the mating surface of Body A
  • Press Body B onto the dowel pins.  Ensure complete assembly with a small hammer, a bench vise, or clamps.
• Tines:
  • Lightly tap four M3x12 dowel pins into Tine A
  • Apply glue of choice to the mating surface of Tine A
  • Press Tine B onto the dowel pins.  Ensure complete assembly with a small hammer, a bench vise, or clamps.
  • repeat for the next two sets of tines
• Full Assembly:
  • The full assembly can be a bit tricky, have patience.
  • insert the Tine Assemblies into the Coil, placing them into the recesses of the Coil
  • With the back ends of the tines spread wide, insert the Body Assembly into the opening.
  • Press the Coil and Tines as far down onto the Body assembly as possible
  • While holding the Coil stationary, pull up on each of the Tine Assemblies - they have a taper to them, and this will cause more pressure, ensuring a stronger hold.

You can use glue in the full assembly step, but I chose not to.  It held securely enough, and I wanted to be able to disassemble the Grappling Hook for additional painting or detailing if ever needed.  As far as glue, I printed in ABS so that I could fuse the sections together with acetone.

For finishing, I used Bondo at the mating joints, then sanded down to a smooth finish.