I would like to know what the mechanism is for building a "click and roll" futon. It is one of those futons that looks like a couch or daybed and when you raise the front up to a 90' angle the back rolls down to make a double or queen bed. When you raise the front again on a 90' angle the back rolls back up to make a couch. What is it and where can I find it. I would like to build my own frame. Thank you for any info.