Driver side door lock

[jax55]

I have a '31 Sport Coupe, but I suspect it is probably the same.
It should be positioned so when locked it will stop the rod from the handle to the latch from moving down (I think). If you look at how that rod works, it will make more sense.
Mine did not have the lock when I got it, but there may be holes already there to mount the lock... I do not recall having to drill holes anyway.