Quality Torque Wrenches.
A torque wrench is used where the tightness of screws and bolts is important. It allows the operator to measure the torque applied to the fastener so it can be matched to the specifications for a particular application.
The technique suffers from inaccuracy due to inconsistent or non calibrated friction between the fastener and its mating hole. Measuring bolt tension (indirectly via bolt stretch) is actually what is desired, but often torque is the only practical measurement which can be made.
Digital Torque Wrenches are available for easily monitoring and measuring the correct torque value to apply onto the nut or bolt when required.