Not to have any interference [Chatzitza] on ones hands: [1]
One may not have any interference on his hands while washing. [Thus women must remove their rings from their fingers[2], and each person should check his hands to make sure they are clean prior to washing.[3]] This applies even Bedieved.
[1] Siddur Seder Netilah; 161:1 and Seder Netila 6 regarding washing hands for bread
Other Opinions: Ashel Avraham Butchach rules that it is permitted to have interferences on the hands when washing in the morning.
[2] 161:7 regarding washing for bread
[3] Seder Netila 6 regarding washing for bread