The distinction between the stuck pipe and the free pipe in a pipe string is referred to as the "free point."
As long as it is not connected to the other stuck joints of pipe below the free point, every joint of pipe above the free point is free, meaning it can rotate freely and be inserted and removed from the hole. Holding a string in your left hand can help you envision this. Grab the bottom portion of that string with your right hand. Since you can move the string in any direction, the middle two thirds of the string above your right hand would be regarded as free. Since no matter what you do to the free string, it will not impact the string inside or below your right hand, the segment of string inside and below your right hand is trapped.
The typical freepoint tool is an electromechanical device used to gauge the torque or strain that a specific length of tubing, drill pipe, or casing has undergone. Bow springs or magnets are used by the conventional freepoint tool to secure it inside the pipe. The typical freepoint tool is run in the hole to 1000 feet above the projected stuck point after estimating the free point using the pipe stretch estimate technique. The instrument is firmly fixed in position. The pipe is then subjected to stretch or twist. The pipe recovery engineer can then use this to get a baseline reading of the free pipe. This will serve as a baseline against which he can measure his subsequent freepoint readings. After then, the tool is advanced about 500 feet past the anticipated stuck place. Readings are taken as stretch and torque are applied. The tool is dragged uphole and readings are collected once more if the tool indicates that the pipe is stuck at that location. The pipe recovery engineer can swiftly pinpoint the precise location where the pipe is free by using the bracketing approach.