In this (5 min) video, I show how two undocumented Civil 3D commands can be used to extend what you can do with AutoCAD Blocks. The first is LINEWORKTRIM which allows you to trim Blocks. The second is LINEWORKDIVIDE which allows you to divide Blocks into pieces without having to explode them.
Learn more tips and tricks at http://civilimmersion.typepad.com
Source: Autodesk