Step1：Zero point at your chosen specific distance, such as set the position as followed picture
Step2：Use the spanner to unscrew the bolt
Step3：Use the spanner to loosen those four bolts
Step4：After loosen four bolt, then tight black cover to the base
Step5：Tighten the four screws
Step6：Cover the turret and set this position to the zero point and tight the outside screw
