There's a windlace piece that goes along the floor that 's held down by the metal strip. Link

The metal strip that goes on the bottom of the door secures the weatherstrip there that goes all the way around the door.
Jerry Kassis covers installation of that metal strip in this video starting at about 15:45.

Kevin
1951 Chevy 3100 work truck
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Photos
1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.