Here's my take on the Arkham Batarang.

This does fold and uses internal magnets to hold the model in the open or folded positions. You will need 6x 8mm diameter by 4mm deep magnets. This model also uses super glue to hold it together so be prepared for that.

To reduce waste and speed up printing time this prints on two plates, plate one is the black parts with the silver highlights only. Plate two is just the blades.

Assembly instructions -

I suggest marking your magnets with a sharpie as the magnet orientation is vital. I put ther magnets in a stck and write a black dot on each one.