Kent-Moore Tools Kent-Moore J-42854 Trim Height Gauge for GM. Y Trim height must be set to correct specifications to assure proper alignment and vehicle handling characteristics. Affix end of tool with magnet to lower ball joint. Align tool so bubble in level site is centered. Tool will be parallel to shop floor. Position metric scale on front or rear control arm attachment bolt. Site along top of the bar to determine trim height setting. Verify measurement with shop manual specifications. Trim height must be measured at both front and rear.