Trail file serves as a backup file into which entered all the steps in defining objects in Creo Elements/Pro (formerly Pro|ENGINEER) If the user makes a mistake in modeling and closes the program, does not have to click all the steps again.
Sufficient if run trail file to create previous steps.
One more suggestion/caution about the use of trail files. Sometimes you use them to recover from an unexpected crash long after your last save. IF this crash was caused by your last action within Pro (as rare as that may be), then you want to delete the last little bit of the trail file before running it, or you will just crash again.
