locking elements 26 each locking element is biased in a radially outward derection by a pair of leaf springs 26a and 26b which are suitably mounted to the lock supporting sleeve by bolts 26c thus when the lowermost packing element is run into the liner 10 and the lock elements 26 are positioned adjacent the annular locking recess 12c provided in the metallic insert 12 in the liner 10 the locking lugs 26 will be urged outwardly into engagement with locking recess 12c but may be cammed otu of such engagement by the inclined surfaces 12d and 12e provided at the top and bottom ends of the locking recess 12c thus the preferred initial run in position of the lowermost packing unit 25 places the locking lugs 26 at a position slightly below the annular locking recess 12c as shown in fig3 a the lock support sleeve 25d is connected to the inner tubular body 25a for run in purposes by an inwardly projecting j pin 25g which is threadably mounted in the lock support sleeve 25d and cooperates with a j slot 25h fig9 provided on the exterior surface of the inner tubular body 25a in the run in position the j pin 25g is engaged in the horizontial leg of the j slot 25h and hence the lock support sleeve 25d moves concurrently with the tubular inner body 25a to the run in position illustrated in fig3 a the tubing string is then rotated in a counter clockwise direction a sufficient amount to move the j pin 25g into alignment with the vertically extending portion of the j slot 25h and tension is then applied to the tubing string to elevate same and this brings the locking lugs.