A 3D face model construction method is disclosed herein, which includes a training step and a face model reconstruction step. The bubble type level of the invention also includes a novel connector mechanism that enables the level to be removably interconnected with the structure to be leveled. A memory module may be disposed on the circuit board. The safety latch has a first position wherein the needle is aligned to pass through the needle opening and a second position wherein the safety latch is moved with respect to the housing such that the needle is blocked from movement in a direction parallel to the longitudinal axis thereof by a portion of the safety latch distanced from the needle opening.