Check out this CATIA V5 tip: http://www.ignitecast.com/p/uTQstXMPZo/
I created and uploaded this Ignitable to IgniteCAST.com to show you how to remove split lines after joining surfaces. This tip is for intermediate CATIA V5 users using the Generative Shape Design (GSD) workbench, so I hope you find it useful.
Steve