Abstract: An apparatus for measuring the length or perimeter of an object has a main housing part provided with a main abutment and forming a main attachment location and a movable housing part provided with a movable abutment normally spaced longitudinally from the main abutment and with a movable location forming a guide. The movable part is longitudinally displaceable on the main housing part so as to displace the abutments longitudinally relative to each other and also to displace the locations longitudinally relative to each other. A flexible but substantially inextensible element has an outer end fixed to the main attachment location and an outer portion extending between the locations, passes through the guide at the movable location, has an intermediate portion guided in the movable part, and has an inner portion extending in the main portion and an inner end.