I'm attempting to install a non-electric bidet for my hubby and when I've turned the water supply fully clockwise, the toilet still functions normally. I've read somewhere in the interwebs that I could hold the float up and flush the toilet to drain the tank and then I could unscrew the tube between the supply and the tank and then finish the install of the bidet attachment... I'm afraid this may make a big watery mess. Anyone have a better idea?

If the toilet shut off doesn't shut off, you will need to shut the water off to the whole house to do your work. I would suggest replacing the toilet shut off while you have the water off to the house, so you don't have to worry about this in the near future.

Thanks for the response! But, that's a bummer. I live in an apartment so I'm not sure where the shut off is for the whole place. I'll see if I can track down the maintenance guy tomorrow, I'm sure he'll loving helping me install a bidet (awwwwkward, haha). Another quick question -what in the heck is that knob for if it doesn't shut off the water supply? I have it currently cranked all the way clockwise... is that okay, or do I need to turn it back counter clockwise some? Thanks again!

I've read somewhere in the interwebs that I could hold the float up and flush the toilet to drain the tank and then I could unscrew the tube between the supply and the tank and then finish the install of the bidet attachment...
You must have misread the article. Unless you shut the angle stop off first the supply will still have pressure and will flood your bathroom. Get management involved. They should bear the expense on replacing the faulty angle stop. Good luck on your project. Tom

J.cans. yep that knob is for shutting the water off, but it sounds like it is just worn out (happens more often than you might think). They have better shut offs for fixtures these days, like ball valve stops vs globe style stops, but they can all fail over time. A new shut off should last you for many years. I would suggest replacing the toilet shut off first, then turn the water back on to the building (to get water back to the other folks) then do your other work.