Thanks for all your kind words! This was, indeed, my first "real" C programming work, although I have dabbled with it in the past, never really got past "hello, world" before...
andpe - bld is right, it's a Yale-type latch, which allows the door to close with the bolt out (actually, the action of closing the door pushes the bolt in, which is why it's handy that it's not permanantly connected to the servo). The milling machine is a Bridgeport Series 1; it's a big beast, but handy. I'll post some links to my workshop, once I've fixed the pictures...
alphabeta - thanks, I'm not sure what effect delay() has on other processing, I believe it acts like a tight loop? Given that, I figured I needed a way to keep the system responsive while the various delays were running, hence the countdowns... If I knew how to do event processing, I'd make them into timed events instead...