I ordered a custom window through a Norandex distributer.

I was going to J-channel around the whole window to accept some vinyl siding.

However, there's this little appendage in each corner of the flange that won't allow a piece of J-channel to sit flush. Without it, J-channel would fit perfectly, so I'm not sure why it's there.

A piece of 1'' wood trim will slide past this appendage (see comparison photos), but it kind of has to dig into the wood, and I'd rather not trim the window in wood.

Does anyone know what this is?


J channel wont sit right because of tip of the flange corner

Could do wood trim

  • 2
    Looks to me like it's just a leftover from the manufacturing process. I would just nip or cut it off.
    – SteveSh
    Commented Feb 13, 2022 at 2:24
  • I would not do the wood trim. That just brings another horizontal joint into play that has to be made weather tight. With that, you have the joint between the j-channel and the top of the wood trim, and the joint between the bottom of the wood trim and the top of the window that would need to be flashed or sealed.
    – SteveSh
    Commented Feb 13, 2022 at 2:27
  • Thanks for the feedback, Steve. What if I put an aluminum drip cap over the wood trim? Whatever I install will be flashed over the air barrier, because I've already sealed that up.
    – Zero Cool
    Commented Feb 15, 2022 at 3:52

1 Answer 1


Distributor stated that this can be trimmed.

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