In putting together my Warhound Titan, I wanted to create a very VERY secure join on the hips of the titan to ensure structural integrity. The joint in question is a ball-and-socket style one, similar in nature to a human shoulder or hip. So, as well as pinning the joint using a brass rod (as pictured below), to create an even better joint, the image shows that I have scored the ball (and not pictured: the socket as well) with multiple strikes of my modelling knife. This is not just in one direction either -- I've created a criss-cross of scores much like the visage of Lucius the Eternal.
Why do this? Well, the scores across the ball-and-socket ensure that the glue grips a whole lot better than it would otherwise do on a relatively smooth spherical surface going in to a smooth concave socket. Not only will the glue run down these scores in rivulets, but the added friction they provide ensures that the pinning I'm doing won't budge a millimetre once its in place and fixed. Its a very simple thing to do, and a technique that I've personally been using for many, many years. But it occurred to me after a conversation with some friends that its not one that might be widely known about. Hence I hope folks out there have found this useful and insightful if they didn't already know about it!