Join duplicated side back on to side duplicated from I have a bag and a side of the bag that I duplicated - they look like this:



I'm trying to connect the duplicated side back onto the side that I duplicated because the other side of the bag has two faces whereas this side only has the one and . 

I've looked around and it seems to be that to connect two objects you have to select a side to delete from each before you can connect them. All I want to do is to add this side back on and connect it to the same vertices it was duplicated from.
Thanks Mr Zak - it worked. 

In my particular version of Blender (2.77) I first had to select the side - select the Magnet symbol, select the Cube symbol right beside it to select the "Snap Element" (Volume, Face, Edge, Vertex or Increment) and then position it they way it needed it.