When I first started building I always used tin snips to cut aluminum flashing till one day a friend put me wise; use a straight edge and score it generously with a utility knife. Bend it till it starts to break, then fold it sharply till it separates. But keep the snips handy to cut any corners. Just an old trick that every handyman knows-or does he? Also aluminum seems to build up on the cutting edges of the tin snips. A dip in turpentine will prevent this; if you can find any turpentine any more.
