Rim help
 

https://cimg6.ibsrv.net/gimg/bikefor...1e1809e71d.jpg

rim has vertical scratch in the middle


so i was wondering what could be causing sudden brake noises when i brake midway,the wheel was just trued and the brakes are in good toe in no screech other than the possible scratch causing it. what can i do at this point?

Post a pic?

I think the "scratch" in your photo is just the rim seam. Rims start out as long pieces of aluminum that are rolled into hoops, and either pinned together (your rim) or welded together and then machined.
If the rim seam has a raised lip that catches the brake pad, you can try sanding it down carefully (not too much).

If this is a front wheel, often all that needs to be done is flipping the wheel around in the fork so the lip is on the trailing, rather than leading edge when it hits the brake pad.

+1. Thanks for mentioning this. It's easier if the brake pad drops off a lip rather than running into the side of the lip.
I always check for this when building a wheel, too (when I can flip a rear rim around as long as it's not yet connected to the hub). Only time when I can't do anything is with an offset/asymmetrical rear rim.