Abstract: Apparatus for determining the inclination of a well bore comprising a flexible rod having an upper end rigidly supported by the apparatus and a needle point means operatively connected with the lower end of said rod and suspended over a vertically movable target. The target is responsive to a predetermined condition, such as time or location, for moving the target relatively towards and against the needle point whereby the needle point will perforate the target to indicate the inclination of the well bore. A weight means is mounted on the flexible rod above the needle point to cause a bending of the rod by cantilever action when the apparatus is in the well bore and when the well bore is inclined with respect to the vertical.