The OP brings up an interesting point that I'll bet that many of us hadn't given much thought too. I know that I didn't.
On mine, my engine hatch is opened by pulling down on a spring loaded latch located down in front of the license plate area. The hatch then lifts with the help of two spring pistons, just like on a cargo bay door. Just off the top of my head, I can't think of anyway that I could lock it if I wanted to. At least, not without drilling and cutting someplace into the rear cap and engine hatch. Not doing that.