Any of the tools -- from the cheap plastic, use once, via the quality replicas, to the genuine Krone KD-1 -- will only fit one way around in an IDC. If using the Krone or replica tool, the cutters would be on the side of the IDC that has the step in its profile.
It is possible to force any of the tools into an IDC the wrong way round but damage to the tool or connector will usually result.
Vince, t.a. Mr. Telephone Supplies on eBay, covers the above in one of his "How To" videos --
[youtube]FFVlhLxy52k[/youtube]