I know nothing about this, but my jeopardy answer is what is threshold weatherstripping. It probably comes in myriad different shapes and sizes.

When i was trying to find new door sweeps and HD and the local hardware store had only cheap stick on plastic junk, I found an online store called Trademark Hardware that had the good stuff. I don’t know what your part is called aside from weatherstripping, but I would definitely check out Trademark.

I think it is more specific than weatherstripping. One of the online images I found that looked similar called it something like ”kerf door seal,” but I could never tell if that is what I’m looking for or not.

I’ll give Trademark a call tomorrow.

If I cannot find a replacement gasket, what would you suggest? Would caulking be a bad idea?

" Would caulking be a bad idea? "

Yes, caulking is a poor idea for that application. If you cannot find a replacement you may want to get a new threshold. I have not seen that part before and any weatherstrip will most likely need to be the same brand to fit as they are not usually interchangeable.

Thanks, millworkman. Regretfully, I cannot get my builder or his construction manager to respond to me so I have no idea where they got the doors. I hope I don’t have to replace the threshold.

There's is no stamp or sticker anywhere on the door with the brand name and number?

" There's is no stamp or sticker anywhere on the door with the brand name and number? "

Most like on the outside of the jamb that buried in the wall. The bumper type sill I have always seen never had weatherstripping that looked like that.

Not a thing on the door or the framework around the door (is that the jamb?). I’ll post pictures this afternoon if I can get good ones that show more specifically what the threshold looks like.

Compression weather stripping? (I googled “parts of an exterior door threshold”). Good luck!

nicksbuilding.com

Maddie, I look at Nick’s before posting here. Couldn’t find what I think I need.

When I searched ”exterior door threshold compression weather stripping” there were many hits. Good luck!

”https://www.google.com/search?q=exterior+door+threshold+compression+weather+stripping&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari

" When I searched ”exterior door threshold compression weather stripping” "

And not one of those will work with that threshold. Every brand is different. That is from a shop that produces prehung units and buys them in bulk, quite possibly from China. You have yet to post a picture or your actual threshold so I cannot be sure what exactly you have.

Thanks, millworkman. Got tied up yesterday afternoon. Pics coming when it gets light here.

Penny for orientation. Arrow in first pic shows the slot.

From interior

From exterior

Close-up

Not as close up.

Unfortunately the pics do not help much as it is impossible to see where the weatherstrip would fit in and the type of "slot" it would fit in. Do the hinges have any brand name (some companies have their own hinges)? Is there a tag maybe on the top of the door? Or anything stamped?

Profile of piece

blue dimension ~3/8”

green dimension ~1/4

Hinges are marked ”HAGER”

Here is another picture using a flash.

I think the piece pretty much fits like the schematic shows in my initial post.

Hager is the hinge maker, no help there unfortunately. I am at a loss as have not seen that type sill but will do some more looking later this afternoon.

Try these guys Quanex.

Thanks, @millworkman. I told my painter you recommended against caulking. We are both curious as to why? He asked if it would make a difference in your opinion if you knew he would be using an exterior silicone caulk.

Not going to do a bit of good, as it is not made for an application like that. May stick to and pull the finish off the door.

PPF, does this show what your are looking for?

I also took a picture with a string in the slot I’ve been trying to show. I tried to lay a drinking straw in it, but the straw was too large.

Do you have a piece of the old seal you could get a picture of?

Does this help?

Without the black cloth

Looking straight down on the portion with fins/flaps. The curved piece is on the bottom in this photo.