the center post 42 in order to prevent rotation of the insert 70 with respect to the center post 42 the insert 70 has a polygonal outer surface 78 which complements a polygonal inner surface 80 of the center post 42 defining a polygonal recess 81 consequently when the center post 42 is rotated it is rotationally locked to the hydrant operating nut 40 the center post 42 has a beveled opening 80 extending axially therethrough which receives the bolt 44 see also fig9 in order to axially fix the center post 42 on the fire hydrant operating nut 40 the threaded hole 45 is tapped through the hydrant operating nut 40 so that the bolt 44 can axially fix the center post 42 on the hydrant operating nut the magnetic detent 50 see also fig7 and 8 is received in a second recess 90 see also fig1 in the top end center post 42 and rests on a rectangular shelf 92 with the top surface 94 of the magnetizable detent being flush with the top surface 96 of the center post 42 consequently when the outer body 26 is mounted on and over the center post 42 the outer body will be freely rotatable on the center post as long as the magnetizable detent 50 remains in the slot in a first position in which it rests on the shelf 92 the outer body 26 fig4 and 5 is secured over the center post by the.