Many 3D printers can handle only a single plastic extruder, and have limited options for "support materials" in order to print overhangs and complex parts. It would be great if you could have a tool which could help you create a 45 degree "underhang" for any parts that need it. This would then connect back to the main body of your part, and let you print the model without supports. This underhang would just be part of the final printed part, adding support to the final model, you would not "break it off" later.