Chaim and Yankel
Chaim and Yankel, two of Chelm’s “less bright” residents are trying to measure a telephone pole. They keep trying to climb it and keep sliding down. Along comes this really big, muscle bound man from a nearby town and says, "Hey, what are you guys doing?"
Chaim and Yankel say, "We're trying to measure the height of this pole."
The strong man wraps his arms around the pole, pulls it out of the ground, lays it down and measures it. Then he picks it up, puts it back in the ground, says "40 feet" and walks away.
Chaim then turns to Yankel and says, "What a shlamazel - we wanted the height, not the length."