the tool is an instrument including a : filament which is brought into contact with an individual to test sensory perception of the individual . when the filament resiliently buckles a standard force is applied to the individual . the filament is retractable within a housing . the filament is mounted upon a shuttle which moves relative to the housing to position the filament either in a stored position within an interior chamber of the housing or in a deployed position outside of the housing . the filament both translates and rotates to move from the stored position to the deployed position . the instrument is configured to securely hold the filament in both the stored position , where the filament is kept safe when not in use , and a deployed position , where the filament is held firm during use of the filament for sensory perception testing .