Sheet metal curve bending tool.
This may belong more in a thread about "technique" rather than "tools" but it is a very crude tool.
To make uniform curved bends in sheet metal I use a length of PVC pipe (diameter varies depending on the curve I want to make). The pipe is clamped to a table and the flat sheet metal piece is clamped down it's center line to the top of the pipe (as shown in the first photo). Then you hand bend it around the pipe as far as you can followed by hammering with a plastic headed mallet (or small steel headed mall) until it conforms to the curve of the PVC pipe.
Then you reverse the process, hammering from the inside of the sheet metal while using a length of steel well casing as your "form", as shown in the second photo.
The last photo shows this length of curved sheet metal attached in place about the door. Further details of using this tool are shown here.