In this shape modeling exercise we take a look at modeling a Twisted Doorknob.
The point of these videos is not to model a complete object but to rather focus on different shapes and issues that you may encounter while modeling. So, essentially, these are exercises.
Hopefully, these videos will help you better understand how to approach modeling certain shapes, and what tools are available in Blender to make things easier.
Download the blend file, reference image, and texture.