House built 1938.Here’s the part on the threshold. Hard to see. Sorry about the dust. The edge of this slips into the channel on the part on the door. Not actually a u on this part.

Its an interlocking saddle and the underside of the door has a lkerf cut out that has a spring bronze wedge shaped pc that fits the threshold.

Here is the jamb weatherstrip and here is the threshold/door bottom.

I concur with Mill-man regarding skill required to install. In the real world,weatherstripping and thresholds in general require more skill than average diyers can muster.

Thanks, I’ve called my contractor. I’m on the list.

You can buy the brass j-channel from Zero International or Accurate. Accurate 21B should fill your need. http://metalstrips.accurateweatherstrip.com/item/door-weatherstrips/door-bottoms-threshold-weatherstrip/item-1093