Materials are .025" diamond plate brass from Precision Scale, diecast eyelets used on Lionel's TOFC cars, brass or piano wire and small tubing. I use stainless hyperdermic tubing 18 gauge but brass would work too. The plate is just cut on a saw then filed and sanded.
The hinged version shown in the thread uses Precision Scale hinges. I saw that style used on some engines in the PRR Museum in Strasburg. Uses fewer items and no drilling required. Shape of the deck is optional.
I think the ones I used are out of stock. These are shown availble.
The early ones I used have a smaller diameter hole for the smaller pins on the ramps. Those pins would break easily so Lionel used bigger pins on the later cars with larger holes in the eyelets. They will work too. If you search on PS-4 you should see most of the flats. Search on all of them as the part number also varies by color so while no black one may not be had, other colors are still available.
That said PSC has eyelets too but are are bit more delicate being made of brass wire.