An instrument includes a body having an interior conduit. A shaft extendsdistally out of the body and is movablebetween a retracted position and an extended position. A locking mechanismthat selectively secures the shaft in the retracted andextended positions includes grooves in the body and a locking nut having pinsthat travel through the grooves to move the locking nutbetween a locked position and an unlocked position. The locking mechanism alsoincludes compression flanges that flex towards andapply pressure/friction to the shaft when the locking nut is in the lockedposition and release/reduce the pressure/friction from the shaftwhen the locking nut is in the unlocked position. The compression flangesrestrict the movement of the shaft when the compressionflanges are flexed towards, and apply pressure to the shaft.
