I just used a pair to install crown molding.  Now, I'm wondering how I would have done the job without these handy helpers.  Very impressive!  I'm not concerned about the strenght of these supports for crown molding.  Still, I would not put much load on them fully extended - maybe 10 pounds.  Fully retracted, they are quite strong.  There were no instructions, cautions, or specifications packed in the shipping box.  I thought this to be very odd as manufacturers are pretty cautious about misuse of their products.