specialist way of displaying on plinth

[Gillthepainter]

Do any of you know what these are: metal supports screwed to a plinth, please?

I went to the Siena exhibit in London, and this particular display struck me.
I have 4 x oldie antique gilded frames, the paintings have not been painted yet. But they would look very effective at a gig I have next yeara, if I could replicate this.
In my head, I can probably make something out of wood? Spray it grey? It's not load bearing, so doesn't need to be metal I guess.

Does anyone here recognise what they are?

[Justintime]

I'd guess they've been purpose made, maybe even on a 3D printer?

[Gillthepainter]

I should think you are right, unfortunately.
I can barely get my 2D printer to behave, so a 3D is beyond me.

[JFeig]

I would just call them a hardware bracket. A bracket for a specialized purpose.

In the case of displaying something in a case in a museum, I would call it a custom mounting fixture or stand.

[theframer]

You could use L brackets and fix them from behind?