an internal collet can be used to lock two telescoping tubes together. in this case the collet is in the form of a truncated cone drilled and threaded down the centreline. the collet diameter matches the bore of the inner tube, having the larger end slightly greater than the bore while the smaller diameter is slightly less than the bore. a threaded stud, anchored at its other end to the tube, is then used to pull the collet into the tube. the increasing diameter of the collet forces the inner tube to expand and be pushed against the inner wall of the outer tube thus locking the two tubes together. the inner tube is often slotted to facilitate this expansion.