Pictures Study Guide Eruvin 58 How does one measure the 2,000 cubits if the terrain is not flat? When does one span the space and one does one pierce it? What is the difference between them? From where do we derive that 50-cubit ropes are used? Why can't they be shorter or longer? What material are the ropes? For the red heifer and the Sotah, ropes were needed - of what material for each? How do we span a space? What if a canyon curves and spanning is not possible? Or if there is a wall? Why is a wall different than a fence? Rav Yehuda says in the name of Shmuel that piercing is only allowed if a plumb line doesn't drop straight down. If it does drop straight down, one would measure just the floor of the canyon. Is there a limit to the depth by which one can measure by spanning? If so, what is that limit? Rava limits spanning to a hill that has a slope of 10 handbreadths for 4 cubits, but if it is less of a slope, one measures the slope itself as if it were the ground. However, Rav Huna brings a different version of this statement that was said by Rava. How does one pierce? Piercing is only used for techumim and not for measuring in a case of a beheaded heifer, egla arufa, or a refuge city because they are from the Torah. The measuring should be done by an expert. If one measure unevenly -  we accept the wider measurement. Similarly, we accept testimony of a slave or maidservant regarding where the border is because the laws are rabbinic, one can be lenient.