[ QUOTE ]
Petzl shunt, and mainly safe operating/work practices
[/ QUOTE ]
I thought that's what you meant. The Shunt was originally designed as a "mechanical prusik" to be used as a rappel safety on single or doubled ropes. It's come to be a popular self-trailing rope grab for rope access technicians on their secondary safety line.
A couple of good research reports on Personal Protective Equipment, including the Shunt, are: