The timing cover and rear cover on GM LS series engines don't have any dowel pins to ensure correct alignment to the center line of the crankshaft. This can lead to annoying leaks at the front seal and rear main seal or may even cause the front or rear cover to crack. These special alignment tools from Aeroflow Performance will allow you to center the front or rear cover when it is installed. It also provides an easy way to install the seal by lightly tapping on the tool with rubber mallet with its plastic construction so it doesn't damage your engine or seal.