Small-scale heterogeneities have long been understood to give rise to contact angle hysteresis. More recently, the question of how they influence contact line dynamics has generated interest. Models that express the hysteresis or dynamics in terms of defect properties exist but have yet to be conclusively tested by experiment. Here we produce heterogeneous surfaces and thoroughly characterize individual defects. Precise dynamical measurements allow us to conclude that there is no evidence of a thermally activated dynamics due to their presence, but that the hysteresis scales with their concentration and the square of their height, as predicted by some simple models.