A trick in the field when you have an odd angle like 17 degrees or something (since so many in my area are owner built--that is not uncommon!). Anyway, where the two walls join, take two credit cards, put the long side of each one against the wall, very, very carefully hold the credit cards in that position, move them very, very carefully over to your sketch pad, trace the angle onto your paper. Pull out your handy, dandy 10@ protractor from your pocket and make a note of the angle. And measure everything possible, length of wall, rise and fall of the angle, distance from the angled wall to a garbage can, then to the porch swing, etc, etc, etc. Then when in the office using Apex, do your exterior wall sketch in free form before attempting to sketch the calculated area. You can make some adjustments in free from, use 16 degrees at 9.9 feet instead of 17 degrees at 10 feet or 18 degrees at 10.2 feet until everything squares up. When you finally have the sketch squared in free from, select your calculated area and follow the dots (join corners). Have fun. Also Apex has a gadget called a Mite-R-Gage, that basically does about the same thing. It looks like two rulers about a foot long that are joined with a protractor.