RoyJ wrote:

I need to make a set of the mounting channels for a neo-angle shower
stall. I have the doors and the side channels, just not the upper and
lower pieces. Gong through the dealer chain just didn't work.

I can get a standard channel section that will work, plan to notch and
weld the 2 joints per piece. Weld area will not be visible so HAZ and
weld material is not an issue. So how do I get a matching polish level
on the new pieces? Is there a surface finish applied when done?

These channels are AL with an anodized finish probably? If so, the short
answer is you aren't going to match the finish short of stripping and
re-anodizing the whole thing. A better plan would be to machine up some
close fitting inserts and screwing the connections together.