“Make me a park!” The message is written on posters taped to a 6-foot chain-link fence. And shouted, loudly, by Lewis Weitzman, a resident of Cambridge. Weitzman is shouting about Jerry’s Pond — a fenced-off pond completely closed to the public, sandwiched between the Alewife T Station and Russell Field in North Cambridge. He's at the pond on a fall day, running a clean-up event with Friends of Jerry’s Pond, a community group he co-founded with Eric Grunebaum. Lewis Weitzman during the clean-up day at Jerry's Pond. (Robin Lubbock/WBUR) “We could create a lot more space here,” says Grunebaum, “and that space could be used for off-road bike paths, meandering nature walks, some boardwalks through the woods. It would improve the natural landscape, but also give people access to it.”