Dear Sam,
Please try the following:
> Have model zoomed out so you can see the main UCS Axis for arafter.
> Use the UCS at object tool and select the UCS Axis comingoutside of rafter web.
> Then rotate this by X Axis to have the Z pointing towards the topof the rafter. X running along the rafter.
> Then use the Bracing tool and Select the required input pointssnapping to node points.
> The bracing element should now be placed at the Centre of therafter web.
Regards