This file is a grasshopper file, meaning you can use it in rhino3D and it will automatically produce the surface; all you have to do is set up the offset table in an Excel sheet in a certain way to accept the file, and it will do the rest, saving you time and effort.-This tool is not for surfaces that have chines in them.-Things you need to do first: Download TT ToolBox from Food4rhino. Download Our Tool. Prepare The Excel Sheet.