The first step was a phone call with a couple engineers where they quizzed me on high level design questions. They asked a few questions about what I saw for myself, but overall, it wasn't incredibly difficult as it was very free form. Next step was meeting with other engineers at their offices to go over designs on a whiteboard. Basically, they would throw out a design and then ask me to change it to make it more robust. From time to time, they would stop me and ask for a deeper explanation. This went on for about an hour. Then a few days later, I met with two non-engineers and went over my work history in detail. Basically, they asked about each place I worked, what I "got out of it" and what I felt they would say about me.Depending on how long you've been in the field, this could last awhile.