ectoplasmosis

Thanks for the recommendations; I was hoping there would be an off-the-shelf product available without needing to go bespoke! Any other suggestions much appreciated.

I'm looking for a way to make a window reveal trim from powdercoated aluminium, as per the example in the attached photo. I can find plenty of extruded aluminium products for dormer roof edge trim, but can't seem to find anything off the shelf for making the window reveal trims as per the photo, even though I can find plenty of examples of this having been done. I must be looking in the wrong places... Any pointers gratefully received!