<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by apirchik:
The reversers are pieces of metal that are pulled from the cover of the engine and places just behind the engine causing the thrust to reverse. </font>
This clamshell design tends not to be used on new engines. While it is very efficient, it is more prone to mechanical problems. Newer engines have sliding panels that open exposing the reversing vanes.