A thermoplastic housing has a chamber open at one end and a thermoplastic rotor is locked axially in the chamber by snap fit ridges and grooves. Two pairs of bores on opposite sides; of the chamber are aligned, with one pair connected by a transverse slot. The rotor has two bores aligned with the housing bores and includes flexible pawl teeth which engage ratchet teeth in the chamber. The teeth rotationally lock the rotor relative to the housing in one direction while a seal filament inserted in the bores is wrapped about the rotor as the rotor is rotated in the other direction. The slot permits the filament to be fixed to the rotor when the rotor is rotated 180.degree. causing the filament to traverse the slot and permit the remaining adjacent bores in the same plane as the fixed filament to be aligned and free to receive the filament free end. The rotor is rotated relative to the housing manually by finger gripped flanges attached to the rotor and to the housing with the filament inserted to wrap and lock the filament to the rotor. The rotor and housing define a channel for receiving multiple turns of filament to enhance the locking action.