From CustomCoD Wiki
This tutorial will teach you very simply how to make shootable pipes, that will create an fx when shot.
1.) Build a pipe that you want to be able to shot, it can be any size and can also be bended.
2.) Now that you have your pipe made, select it and right-click in the 2-D grid, go to script and select brushmodel.
3.) Select your pipe and press n , and now give it a this key and value below.
Key: targetname Value: pipe_1 (Note: This step is optional and just makes the pipe easier to select through search and find object tool.)
4.) Now you have to choose what kind of fx you want to come out of the pipe when shot; steam, water, or fire. When you choose give it these keys and values.
Key: script_noteworthy Value: (steam, water, or fire) without parenthesis.
Thats all, now go have fun in radiant.
Speacial thanks to CustomCoD member VT-Ownage for this tutorial