I made a quick and dirty version of Izaya’s flickblade knife to go with the other Durarara items. I didn’t thoroughly photograph the process, unfortunately.
For the most part, the blade is many layers of styrene laminated together and painted. I used a textured styrene (for model train buildings) for the grip. The rotating blade mechanism has two rare earth magnets embedded in it. One or the other of these is always connected to a third in the handle. This allows me to firmly hold the blade open or closed. The edge of the blade is made with craft foam to make it safer to stab people with it. The knife comes in three pieces which screw together.