as an instant emergency fence repair
use expanding trellis (a couple of quid from wilkinsons , poundstretcher or a garden centre like B and Q) covered with a sheet or towel and attach the trellis with twist ties/string to the top of the fence(so they don't get out through the gaps). If the panel is in the centre of a row you will also need sticks of some sort at the sides, to keep the panel upright with the trellis- long wooden spoons would do.
hope this helps - sue:wave:
and I would consider 4ft a minimum fence height -some rabbits will clear more depending on size and their age.