OK I figured it out. But it seems a little counter-intuitive considering what UC shows you on the screen. As I understand it the default mode is acting on blocks of lines. If Line Mode Merge is not active the "Merge First to Second, and Merge Second to First" arrows will merge the whole block. I get that. If Line Mode Merge is active, and you select the line you want to merge you'll see the arrows/icons for "Merge First to Second Before", "Merge Second to First Before" etc become active which is what confused me. I didn't want to merge the line before or after the corresponding line in the second file. I want to overwrite it with the first file's line. You need to right-click or use the icons in the toolbar to merge the individual line. I hope this makes sense.
Here's what I did: Activated line mode merge. Then right-mouse click on the line you want to merge and you will see a couple of options: "Merge First to Second" and "Merge Second to First", or use the icons up there on the toolbar. Voila! It works. I've attached an image. It might be too huge but I just grabbed it with SnagIt, annotated it and attached it.
Seems to me that task as simple as this that spawns a thread on the forums should be revisited or documented more clearly.
- UC Merge.png (41.4 KiB) Viewed 2460 times