For accurate linewidth measurement in scanning probe metrology the shape and size of the probe tip must be known. Since the probe can be degraded during a scan, quickinsitucharacterization is desirable. A technique is described employing an array of known structures that allows tip characterization with the probe microscope itself. This technique can be used to measure either the shape of a probe tip or the flexing caused by attractive forces near a sidewall. The results suggest that the sharpest probes may experience significant bending in the vicinity of a wall.