Switchblade Key Holder

thingiverse

I recently crafted this device through mechanical drawing last year. It basically encases a key and when you release the sliding lock (bolt), just give your wrist a flick, and out pops the key. Now engage the lock to prevent the key from retracting again. Don't worry if not all the files are needed - experiment with it. The central layer should consist of multiple layers of balsa or bass wood so you can adjust the key thickness as desired.