Today, I will show you how to create a LEGO Technics Balisong knife. Unfortunately, I had to obtain most of the parts through the LEGO Mindstorm kit, which is relatively expensive to purchase, though I am sure you are able to find the parts through many other LEGO kits.
As this is made of LEGO, this shouldn't be illegal in your country and has no sharp edges. The only way you could get injured is by severe squeezing in the handle, which is almost impossible.
Step 1: Collect Parts
The parts you will need for handle:
6 cross spacers
2 '5 hole space' axles
4 '14 hole' no stud bricks
After you collect these, follow the pictures. You need 2 of these handles for the knife.
Step 2: Make the 'knife' Part
Parts needed for knife:
2 '3 slot' friction snap pegs
1 cross block
1 '3 hole' axle
1 small axle spacer
1 180 degree angle element
1 '7 hole' axle
Sorry if these names are hard to understand but I got them from Lego Digital Designer, unlike the previous step because I didn't know the names.
Knife and handles should be pretty simple to assemble, use pictures for guide.
You are now finished. I will be developing a holster for the balisong knife soon.
Thanks for viewing, I hope you enjoy it.