The Simpleframe 120 (120 is a reference to the amount of needles) is designed to be used on your lap or across a chair it. It offers single and double bed variations and boasts that it does a variety of stitches but it takes a good deal of patience and has an annoying clack clack noise during operation - so not very comfortable for any poor soul sitting next to you, in the case of the 120 model it also has an attachment that allows you to knit stocking stitch.
Take a look at the youtube video by its inventor Dr P J Reilly
I paid around £30 for this machine and would not part with it if only for its curiosity value- they seem to be going on Ebay for an inordinate amount of money now - since doing a bit of research on this machine - the model I have is one of the biggest models but not necessarily the best as its too long to be comfortable to sit in the lap - I still could not imagine anyone sitting for hours knitting with this beastie but once again though, a collectors piece that had quite a following in its day.. They sold quite a few different models, from a tiny machine that sat comfortably to the larger bulkier machine photographed.
There are a few videos on youtube and this is one featuring the inventor
Dr P J Reilly on https://www.youtube.com/watch?v=i2vH7qCL7so
He makes it look so easy and there were many photographs of knitter in the days when it was invented sitting around knitting stuff. The box on my frame is looking rather worse for wear now and the machine itself has weathered the humid conditions of the knitting shed. I do get it out now and again for a bit of play to see if my experience with machines over the years makes it any more fun but no, to me it really is a museum piece - how folk produced on this I will never understand - but you know me, the patience of a gnat!