How to open a sofa bed

A friend of mine was recently telling me how they bought a sofa bed. They had no idea how to open it or use the fold out bed inside. There were obvious ways they tried, but it was not intuitive the way in which the bed opened. After about an hour of pushing and pulling various tabs and labels and strings and straps they eventually got the bed opened. And can you guess what fell out of the middle of the sofa bed once it was opened ...

Instructions on how to open the sofa bed.