wrote
I have acquired a roll of aluminum that is about 12 in. wide. The tin
shears we inherited are not sharp at all. What I want to do is cut it
into strips and would love to find a way to lay it flat and cut it with
sharp knife or something. Husband says he doesn't think that will
work. What do people do who need straight edge - long strips? Thanks.

No doubt you probably do not have access to a brake for aluminum, so make
due with simple tools. Word of caution, aluminum and the tools I'm going to
tell you to use, can cut you. Handle with care.

If you're cutting multiple pieces the same length, cut the length first.

On a concrete floor or drive, uncoil the stock approx. one foot longer than
needed. Set a weight (stone.brick, board, anything) on the end, and a
weight on the other end near coil. Make sure the concrete doesn't have
debris between the stock and the surface, aluminum stock will dent easily.

Place a check with a pencil on each edge for the desired length. Use a 1"x
material for your straight edge, or a framing square. Line the straight
edge up with your marks, hold in place with a knee, take a _sharp_ razor
knife and run along the straight edge on the aluminum using slight
pressure. Pull the knife towards you, you can make two passes, but usually
one pass will do. Remove the straight edge and weights, you'll want to bend
the aluminum reverse (backwards) of the cut. The aluminum will snap clean.

You'll want to make sure you don't kink the aluminum, I always found it
easier to cut and snap in the shade instead of the sun, even using a brake.