  Orientifolds of the type IIB superstring that descend from F theory and M
theory orbifolds are studied perturbatively. One finds strong evidence that a
previously ignored twisted open string is required in these models. An attempt
is made to interpret the $J$ type torsion in F theory where one finds a
realization of Gimon and Johnson's models which does not require these twisted
strings. S-duality also provides evidence for these strings.
