Q&A Side Leg Height

Don't over think this one.

The side leg is just the straight side of the vent in an upright position.

So to get this measure, place the end of the tape measure at the bottom side of the vent or opening.

And stop the measure where the side upright stops and the top turn or angle starts.

The Cathedral style vent has a triangular top mimicing a gable.

Do not measure the top angles.

For an opening size measure, the measure stops where the framing stops going upright and changes to an angle.

The Tombstone side legs are measured the same.

Stop the measure where the arch starts.

And again, here, where the framing changes from straight up to start curving.