It the Leatherman has any knife blades longer than 4 inches it is a prohibited item, which means it will be disposed of prior to boarding according to official policy. More likely they would confiscate it and return it on debarkation day.
But by my reading of Carnival's policy as long as the Leatherman meets the knife length requirement it is okay.
All luggage is x-rayed so it doesn't really matter where you put it. I'd probably leave it in my checked luggage.
Yes, I assumed when you said a "small" Leatherman you meant it. I have a very small one that I bring on each cruise. It was meant to go on a key chain and has a small pair of scissors and the small screw driver blades and a maybe 1 inch blade on it.
================================================== ========== Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013