There is a little metal strip as mentoned above. Take a good look at it to see if some previous owner "opened" it up pehaps to try do the same things your doing.

IF it like my 52 that little strip it goes in will have a place in the center to slide one end into the channel. Then pull it all the way to one side until the other end is in the channel and then just pull it straigth back through the channel.
Usually the new ones are a little long and you have to cut off a short piece so it fits snug end to end.

....IF its the same as my 52


1937 Chevy Pickup
In the Gallery
1952 Chevy Panel
In the Gallery
More photos
1950 Chevy Coupe
Pictures!

I'd rather walk and carry a Chevy hub cap than ride in a Ferd.
I can explain it to you, but I can't understand it for you smile