US Patent 7703817 Unitized security seal

A unitized security seal having a shackle, an engagement housing with a passage for receiving the shackle, and at least two locking members spaced along the shackle with undercut openings to the outer surface of the locking members, at least one pin being located within the housing passage and oriented to engage the undercuts as the shackle is advanced through the passage to provide non-removable engagement of the shackle in the housing, and at lease one undercut including a frangible member positioned between its entry and its exit for engaging an engagement housing pin to resist removal of the shackle from the engagement housing until a sufficient force is applied to shear away the frangible member.