Hi Martin - if you have pieces that have edges that are directly on top of each other then you can use Edit > Join. If you're going to do that you would want to delete the end caps of the pieces (or not generate them in the first place by disabling the option in Sweep) before copying them so that the edges to join are open and not already connected between 2 surfaces.

Boolean Union would probably work too, but the booleans generally try to do a kind of more complex task of finding intersections between objects and then cutting them up and removing some material.

If you don't actually need any material to be removed like when you've got surfaces sitting next to one another with their edges actually touching each other then Join will glue those together with a lesser amount of computation than the booleans.

If you've got something like 2 objects that are pushing partway though each other, and you want to combine those, then that's the kind of thing where you would definitely need to use Boolean Union since you would want some intersections between the different surfaces to happen.

- Michael