Actually, this tool is a gem that was designed by a car inspector who knows all about NJS standard machines as a prototype, and took care of shape confirmation, trial, and feedback. The checker is used as a gear to handle the car inspection before the busy race. It is also a tool nominated by head mechanics in New Zealand and Denmark as a tool to be used at the Tokyo Olympics
It is a new type of tool that has never been seen before, checking for looseness and attaching / detaching a 6 mm wide square nut attached to the connecting part of a truck chain such as the Izumi V chain. About half of the people who use this truck chain may have experienced that the square nut was loose or lost when they noticed it. Check the nuts with a checker just before the race, before going out, and during breaks during the ride. Work by pushing vertically toward the nut, and the knurled handle provides comfortable torque control.