"Univalve" is a word in ENGLISH

A blind man was describing his favorite sport, parachuting. When asked how this was accomplished, he said that things were all done for him: "I am placed in the door with my seeing eye dog and told when to jump. My hand is placed on my release ring for me and out I go with the dog.""But how do you know when you are going to land?" he was asked. "I have a very keen sense of smell, and I can smell the trees and grass when I am 300 feet from the ground" he answered."But how do you know when to lift your legs for the final arrival on the ground?" he was again asked. He quickly answered: "Oh, the dog's leash goes slack."