I made one of these once and it worked great.

what I did was first find an old ink pen and snatch the spring out of it. I then took a thick rectangular piece of brass and drilled a small hole into it big enough for the end of a paperclip. then I slotted a small piece of wood the width of the spring and glued the brass to it. I then narrowed the brass frm abt half way down to the end I eanted to latch. then inside the hatch I built a little box to hold his. the narrower part of the box will stop the catch from falling out but be sure to allow enough so it will drop and latch. then just make a small slot in the hatch. then all ya have to do is use a paperclip or something to poke in the hole and slide it up.

I dunno if my explanation makes sense or not but if it dont let me know i will see if i can explain it better.

Joe