Mark out map from shp data

Hi everybody, 

I'm new on Grasshopper, for my project i would like to work with HSP data from "NYC opendata". 

I've just download "buildings curves", all is good but i would like to mark out the map, for have a little part of data. 

I search the solution, i have try to use bollean whith a surface: no way. I would like some help :)