I couldn't find a suitable door threshold, so I made one

In my area I see old beds thrown out pretty regularly. I try to collect the bed rails since they're usually made from a single piece of maple or oak. I've made a few thresholds from them.

That is brilliant!
- Waste not want not.

Looks better than anything you could've bought at the store; nicely done!

Thank you Friend!

Showing any type of skill at craftsmanship is veering way out of dull territory.

I may have to go lie down for a bit.

not dull at all!

Nice work!

Very nice

Very nice! How did you go about it?

I picked up a piece of hardwood that was 5/8 inch thick. Just measure the gap under your door so you know how tall the threshold can be. I went with a 3.5 inch width to cover the floor's expansion gap with room to spare. I just cut that down to the width of the door. Then I used a router to put a 45 degree chamfer on all 4 sides.
The 45 degree angle goes down about half way, I just ran a scrap piece through the router and progressively raised the bit until the angle felt right, then did it on the final one.
Gave it a light sanding to remove any splinters and then I just stained it to match the floor and used a rubber mallet to get it in place. It's pressure fit, so it's a little tight to hold it in place. Some people opt to screw them into the floor below instead.
- Dropping a few brads/nails into it to hold it into place is a good idea. As time goes by, wear and expansion/contraction of the flooring will have it popping out.
  I picked up an airgun to put in 2 1/2" finishing brads on the floors I did (engineered hickory). Turned the air pressure up to the maximum the gun was rated for (150psi) and sunk the brads into the board

Is that treated/engineered bamboo laminate flooring? I think I have the exact same stuff from Home Depot.

Sure is! I got it from a local flooring store and installed it myself years ago. It's hard to beat the price and hardness.
- Yeah, I put mine in 8.5 years ago, and with a large dog, 2 cats, and 3 kids, it's held up remarkably well. The only problem I've run into is some of the tongue-in-groove connections have pulled apart over time creating small (maybe 1/4") gaps, but the planks themselves have been great. And frankly, that is probably a combination of installation error (by me) and us living in a pretty harsh environment with a huge number of freeze-thaw cycles and lots of snow every year (with a shitty insulation job in our crawlspace).

I'm just wondering, is it common to have that big a gap under your doors where you are?

I'd stub my toe on that, fuck me 😂

These thresholds are usually about 1-2cm raised and have sloped sides to specifically avoid catching toes.
They're very common in north America