One of the downspouts from a roof job done a year ago drains right into
the soil next to my foundation. I was thinking of making a drain-away
out of concrete (a bit of concrete work needs to be done right there,
anyway), but I got the idea of routing the downspout out away from the
foundation horizontally.

When the roofers did the job a year ago, I salvaged a couple of extra
10' or so lengths of aluminum downspouting and stashed them in my
garage. I figure I can run a 4' or so length of this from the end of the
downspout coming from the gutter above and route the flow out a few feet
from the foundation and onto my concrete patio where the water won't
sink into the ground at the foundation.

How can I cut the aluminum? I guess I can work it with a box cutter, but
I wonder if that's best. The metal is sure to deform if I cut it that
way. What do the pros use? TIA.

Dan