I posted before, but it looks like the forum ate my post! We have French doors that lead out to the patio. There is a 1/4" gap under the doors, so air, bugs, and even worms come through. We also discovered water in the metal track of the threshold, almost up to the level of the hardwood floor during the recent rain.

I checked a set French doors in another room and discovered they have a rubber base that runs the length and width of each door, however, that rubber piece is attached via two 1/2" grooves the underside of each door. The patio doors have apparently been shaved down, because the grooves are only 1/8", if that. What can I use to seal these doors?