The signs for the letter "R" and the letter "U" are similar in the fact that two fingers are used BUT:
O the palm faces inward for the letter "R" but outward for the letter "U."
O the fingers are crossed for the letter "R" and are held straight together for the letter "U."
O the letter "R" is drawn in the air while the sign for "U" does not incorporate movement.
O "R" is signed by curving your fingers downwards while "U" is signed by curving your fingers upwards.