No curved frame work is required.  Simply use the below diagram and Specification Chart to determine Framing Block dimensions.  This can easily be done by:

1.  Measuring your rough opening width (the distance between the framing studs).
2.  Follow the Rough Opening Width Column on the Specification Chart down until you find the Model that your measurement corresponds with.  This Model # will be used when ordering.
3.  Bring down the corners of the opening using the corresponding Framing Block dimensions with 2x material or plywood flush with wall prior to sheetrock.  The Elliptical unit can be nailed to the header, therefore the corners do not need to be structural.

All dimensions assume a 1/4" tolerance

• The top of the capital block can be placed at any height by installing header at 13 1/2" above the desired capital height.

• Rough opening needs to be placed 6 1/4" away from a corner to allow for the capital width.  If two openings meet in a corner, rough opening needs to be 8 3/4" away from corner.

• Capital Vertical Height is 2 1/2" and extends 1 1/2" beyond casing.

• Elliptical Casing extends a maximum of 4 5/16" above rough framing header excluding optional keystone.