There is more to roofing than just nailing down shingles. A roofing system must also adequately ventilate the attic space. Proper roof ventilation prevents shingles from curling and reduces energy bills.

Even the most skilled carpenter can make an error, but just because an error occurs, doesn't mean the job is ruined. If you make a bad cut on an angled piece of moulding, correct the error by making a clean cut on the inside of the defect.