I made a quick and ugly mock up of how my locks and tracks will work.
I have a load of stainless steel H channel laying around and I intend to use that as a guide to deploy and retract the knife.
The blade sits inside of two 2″ sections of H channel, that channel rides inside of the outer channel. and is turn keeps the blade tracking straight out.
After working on the channels and getting everything to track straight I cut them down and threw some quick ugly welds to hold them together.
The thing that seems to be sticking up (lower rail in the picture) is the locking mechanism. It is normally open and will be engaged/dis-engaged by the slide. The slide will rest on top of the lock and keep it engaged until the trigger is released, it will then allow the knife to travel freely until the slide trigger is released at which time it will return to an engaged position.