As stated already they are required for fitting either 'Fly', 'Clear Sports Fly' or 'Roadster' and the slightly smaller 'Summer' screens. There was also the 'Classic' screen that some say was taller than the current "Roadster' one but I would ask for measurements.
The factory OEM fork fixing kit consists of 4 fork clamps with threaded holes to accept the 4 bolts that hold the fairing brackets in place
There is an alternative 'fork tube' style available from an Dave Gill who has an aftermarket UK online shop Rocke's Patches or his eBay site Toyota6510 . These need to have the fork tubes removed to fit though, which may dissuade some.