One of the simplest arch trim pieces to measure.

The base measure is of the window (or window trim if present).
This is across the bottom of the arch.
To locate the base on arched windows that are over square windows,
mark where the arch starts with tape or a string to keep alignment.

And measure up the center from the same base mark.

And, of course, the depth the Half Round J Channel needs to be.
The depth is marked on the order as (D).
The width of the face (A) can be applied to the order form as well.
The flange on the rear will be 1 1/2" wider than the face to use as a nailer.
By installing the arched j channel first, this will align the leg placement easier.
The trim piece will come a couple inches longer than needed.
Just trim to fit.
If applying legs under the half round,
slide the side j channel legs over the arched ends with the curved ends inside the straight legs of j channel.
Easier without having to tab the j channel out to direct the water flow down and out.
The trim piece will come a couple inches longer than needed.
Just trim to fit.
If applying legs under the half round,
slide the side j channel legs over the arched ends with the curved ends inside the straight legs of j channel.
Easier without having to tab the j channel out to direct the water flow down and out.
More answers can be obtained by
Calling 901.281.2887
Emailing contactus@onyxxteriors.com