I have found that the Lansky"dog bone"triangular style very good.I carry one when ever I go afield.It has sharpened every thing from multi tools and SAK's to Kabars and my A.G.Russell One Hand Knife(AUS8A Steel)with good results.They are not exspensive,only five or six dollars US.They are not very big either at about 4"x3/4",still small enough to carry in a pocket.The Lansky system is also a good
investment also.
Boatman