E FIXED CONSTRUCTIONS
E21 EARTH OR ROCK DRILLING; MINING
E21B EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
E21B23/00 Apparatus for displacing, setting, locking, releasing or removing tools, packers or the like in boreholes or wells
E21B23/02 for locking the tools or the like in landing nipples or in recesses between adjacent sections of tubing