You can block 1035 damage, but regularly only 50% of incoming damage can be blocked, so it's 1035 or 50% incoming, whichever is lower.
Knights can go above 50%, up to 82%, so damage reduction (armors, shields, accessories) gives more bang for their buck for Knights. In turn Knights don't have to slap as much armor as others, or alternatively, they can wear full-tank gear and receive relatively small amounts of damage even from high-lvl mobs dealing criticals.