Probably something relatively discrete. You could use a series of posts with chicken mesh stapled to them or if you do want to go for a more structural type, then a small picket fence (you can buy pre made sections at many garden centres). You don't say how big your dog is or how high it can jump?

Thanks for the quick reply.

The dog is a German Shepherd and the conifers are around 12 feet so the dog jumping is ok.

The problem is she goes below the conifers and stakes out her territory as we hav a slatted 8ft fence the other side of the conifers.

It is to stop her going below them and run up and down behind them.

We thought about Chicken wire but went against this as we thought it wouldn't look nice.

We have green mesh behind our conifer hedge, and that stops our Labrador from getting through. It fits in well with the garden, and it's unobtrusive. You could fasten it to the existing fence, at either side, whichever looked better. You get it at the Garden Centre off a roll.

Ooops! Nearly forgot to say 'Welcome to GoY'!)

you can get chain link now that has green plastic coating or a green welded mesh to . the other option would be to get the chicken wire and some green spray paint and it will dissapear into the background . excuse my spelling .ow and hello bye the way lol .