The differences between these types of lines can also be looked at in the following way : the distance between asymptotic lines run to zero in one direction and grows without bound in the other ; the distance between ultraparallel lines increases in both directions . The differences between these types of lines can also be looked at in the following way : the distance between asymptotic lines shrinks toward zero in one direction and grows without bound in the other ; the distance between ultraparallel lines ( eventually ) increases in both directions .