PurposeTo describe the use of a ruler to increase the accuracy and customization of Lester Jones tube placement.Materials and methodsThis was a review of 92 patients who underwent minimally invasive conjunctivodacryocystorhinostomy using this instrument.ResultsThe success rate was 100%, with an average operating time of 15 minutes. In nine patients, late migration of the Jones tube into the nasal cavity required a secondary intervention, with successful Jones tube repositioning. In five cases, obstruction of the tube opening was caused by conjunctival overgrowth.ConclusionThe millimetric ruler engraved in the sleeve of the trocar allows measuring and placing a personalized tube for each patient.