a tool for multiple purposes features one ore more dogs that can engage a collar groove or restriction sub in the wellbore . the dogs are extendable through a sleeve biased in opposed directions and are supported from a mandrel . the dogs can retract into mandrel grooves to clear restrictions on the trip into the well . on the way up to a collar that has just been passed , the dogs engage and an upward pull on the mandrel displaces fluid through a restriction to allow enough time to get a meaningful surface signal of the overpull force . thereafter , the applied force can be reduced as the dogs release at a lower applied force to reduce the slingshot effect . the tool can be inverted and used to keep a constant force on a bottom hole assembly during offshore drilling where a heave compensator is employed .