I agree with many of the lower star ratings. First point is that the screws supplied are completely useless, the slots quickly disintegrate when attempting to fix the brackets. Don't try to use them. There are probably too few of them as well. Second point, the instructions lack detail in all the vital points, e.g. it tells you to measure the handlebars to saddle but then not how to apply the measurement to the gap between the brackets. You have to judge this from the fuzzy picture but maybe an exact measurement is not material. Also, I ignored the advice the feed the "rope" through all the mechanism before starting to fix it to the rafter. Just tie a good knot in the saddle one end and thread it through after you have fixed both brackets. It must be easier than have all that string wrapping around you as you fix it up.
However, once fixed the system works fine (well after a week or so). Some people have said it doesn't pull evenly but if you pull it up a bit the front rises, if you then pause, the back comes up and the front goes down, equalising the load. It does this up to the top.
All in all a neat idea executed with poor quality materials. But for less than £10, it's hardly surprising. I would buy it again.