In reply to Cheese Monkey:
Yes, that sounds about correct. It is also useful on protectionless traverses, especially where the hard move is just after some gear (for the leader) before a long runout, thus making it serious for the second. You may need to leave a piece of gear and/or a biner. I usually lead the route as usual and leave it up to second to rig a back rope if they want, if that means leaving a piece then so be it.
As a leader you can also traverse back above a bold traverse from higher up the climb to place a piece off route, creating more of a toprope for the second. Look at some photos of Voyage of the Beagle on the Dubh Loch as people often employ several of these techniques for the 'Voyage' pitch on that.