To Form a sushi roll, cut Nori to the size needed for the amount of filling. A single ingredient sushi roll, such as a cucumber roll, requires a half sheet. Place the Nori lengthwise, shiny side down on a bamboo rolling mat. Dampen hands with water and spread the sushi rice just to cover the Nori, leaving a 1/2 inch margin across the top. With your finger spread a dab of Wasabi along the center of the rice creating a grove. Lay the filling of your choice in this grove. To roll, hold the filling in place with your fingers as you curl the mat forward with your thumbs until the tow ends of the nori overlap, forming a cylinder. Apply gently but even pressure to the rolling mat. Remove the sushi and cut it into to 6 pieces with a very sharp knife moistened with water.