Door bottom seal

Fern Bench

Last week during frosty weather I went to open the front door but it was kind of frozen shut. I pulled it with a bit of force and it opened but the seal came away from the bottom, there was a black strip trailing out from the underside of the door.

I managed to nudge this back in to its slot, but I noticed for the first time that there's another slot parallel to that, closer to the outside. This slot is empty and looks like it would take another sort of strip.

The door has always been cold, and in our otherwise snug new-ish build (7 years) it has been the only point where we've felt a chill in the mornings. Over the few years we've also noticed small amounts of water sitting in the channel under the door after heavy rain. It's extra wet today as I had it open while fixing the seal. And storm Isha.

My questions are, Is this slot designed to take an extra seal?

If so, why was it left empty?

Should and can I buy some sort of a seal to put there that would improve insulation and waterproofing?

Thanks a mill.

whizbang

No seal. Its a drip channel, Specifically meant to break any flow of water back under the door. Water hits this and drips oway.