And then cutting it so you have one piece that looks like an upsidedown l the long leg of the l would go down either side of the transom and the short leg across the thickness of the transom.
How to bend 4mm aluminium sheet.
Lift the clamp bar away from the rear of the brake frame and slide the sheet in perpendicularly to the direction you want to bend it.
Most frequently expensive sheet metal bending tools called brakes are used to bend sheet metal but you can also complete this task without one.
Then place the clamp bar back down on top of the aluminum crosswise.
Insert your aluminum sheet into the brake beneath the removable clamp bar.
Place the aluminium sheet on a work table.
When you release the handle the bent material will spring back to 90 not 85.
How to bend sheet metal without a brake.
How to bend sheet metal without a brake in 4 different methods with minimal or homemade tools.
If you are set on trying to bend it you could try bending it 90 deg.
Set a fire extinguisher in the area you will work in.
Bending sheet metal by hand is a manageable task if the piece of sheet metal is small and thin enough to handle.
Make sure the bar is seated firmly inside the frame.
The two m10 bolts in the top are to clamp the sheet between the backstop and the base.