This is not such a silly question,I only found out how to fully lock my '50 fairly recently.

I knew of the single passenger lock (obviously) but I would lock the drivers side,scootch over the seat then try and lock the passenger door with the internal handle before I shut the door,then try to lock it with the external keyed lock......DUH!
Needless to say this didn't work so I just left it unlocked on many occasions...

I've only had the truck 11 years...... blush

1950 Chevy Advance Design 3100 in Scotland
In the Stovebolt Gallery
More pix on Flickr.
I've definately got this truck thing in my blood ... my DNA sequence has torque settings
"Of all the small nations of this earth,perhaps only the ancient Greeks surpass the Scots in their contribution to mankind" Winston Churchill.