Help with joining parts of a model using boolean modifier I'm trying to merge together two parts (the ones in the images) of a model using a boolean (union) modifier, but I get an error saying "Unable to execute boolean modifier". I browsed around a little but couldn't really find an answer which worked in my case, so I'm wondering how I can get the boolean modifier to work ~
The problem was non-manifold geometry as mentioned in comments. After making mesh manifold Boolean modifier worked properly.