In situ ulnar nerve release has been gaining popularity as a simple, effective, and low-morbidity procedure for the treatment of cubital tunnel syndrome. One concern with the technique is how to manage the unstable ulnar nerve after release. It is unclear how much nerve subluxation will lead to problems and surprisingly there is no grading system to assess ulnar nerve instability. I propose such a grading system, as well as a new technique to stabilize the unstable ulnar nerve. The blocking flap technique consists of raising a rectangular flap off the flexor/pronator fascia and attaching it to the posterior subcutaneous flap so that it blocks the nerve from subluxation/dislocation.