Bolter,
The hint is in the SU User's Guide: here (go down to "Folding Along an Axis of Rotation"):
http://download.sketchup.com/sketchuphe ... Rotate.htm
According to this method, you first
place the cursos (and click) on any of a point that's on the axis of (the desired) rotation,
Wiothout releasing the left button, you start dragging your cursor in the desired direction - of the rotation axis (let it be a "regular" x/y/z axis - when it changes the colour, as well - or any other line whith which you'll have some inference with)
3( Then releasing and choosing an appropriate point in the selected geometry to rotate - either by snapping it or entering precise values into the VCB.
That's all - but if I were you, I'd experiment with these (new) tools a bit before applying them on "serious" models.