Abstract: An improved obturator for safe deposit boxes and the like is integrally manufactured from a resilient synthetic material such as nylon. It includes a substantially flat head member having a rail member cantilevered perpendicularly from one side thereof. In the preferred embodiment, the rail member includes three elongated arms each joined at both ends thereof to transverse end and distal end members. One arm, centrally positioned, is straight and serves to limit the maximum spacing between the said transverse end members, while the upper and lower arms are provided longer than the one arm and bend outwardly, flexibly and resiliently, on opposite sides of the longitudinal plane of the central arm. This permits the longer arms, when flexed, to contact opposite interior portions of the key hole channel to frictionally resist withdrawal, and to also engage lock tumblers in the keyhole channel, thereby preventing accidental obturator withdrawal.