These photo steps show that it can be done using a utility knife.
Cutting aluminum sheet clean.
Clamp the aluminum down.
If you use metal shears to cut thin sheet metal such as duct metal it curls and can be difficult to flaten properly.
Probably the preferred method for cutting intricate or thick aluminum the water jet focus a very thin stream of water mixed with abrasives at extraordinary pressures and very high speed into the sheet metal.
2 mark the start and stopping point of your cut.
The illustrations are for a small bracket but i have cut 3 foot.
This weakens the aluminium and creates a fracture line.
With the aid of a straight edge and a sharp knife score both sides of the aluminium sheet.
This jet of water eats away at the metal and leaving a clean smooth edge.
How to cut thin sheet metal and keep it flat.
Sheet aluminium can be cut without the need for a guillotine or tin snips which tend to deform the metal.