Switchblade Key Holder

This a device I made in mechanical drawing last year. It essentially house a key and once you disengage the sliding lock (bolt), you flick your wrist and the key pops out. Then engage the lock to keep the key from retracting

Not all of the files are necessary, so play around with it. The middle layer should be several layers of balsa or bass wood so that you can adjust for the key thickness.