A uterine manipulator includes a shaft configured to be inserted into a cervix and a colpotomizer assembly configured to move along the shaft. The shaft includes multiple ruler markings printed along a portion of the shaft. The colpotomizer assembly includes a sleeve that includes a rotatable locking member configured to compress the shaft in a manner that locks the colpotomizer assembly in position along the shaft when the rotatable locking member is depressed against the shaft. The rotatable locking member includes a cam roller configured to compress the shaft when the rotatable locking member is depressed towards the shaft.