Barchester

I haven't given any measurements because this method can be used for any scale and is equally effective. The two white lateral bars you can see are of thick card, as are the upright posts. I work on a sheet of glass and apply the smallest touch of paper gum, or Pritstick or similar, to each end of the lateral pieces and then stick them down on the glass the required distance apart. This distance isn't critical because they will be covered by the front planks. Just make sure that if both sides of the fencing can be seen that any added lengths are of the same dimensions and that they line up with each other. If you don't work on a sheet of glass then a simple jig will answer the same purpose. Once the laterals are stuck down, or in the jig, then add the posts, more thick card, at the required distance apart. These measurements are more a question of what looks right to you rather than of scale distances, unless of course you are making 6 foot panels then the measurements just need converting to your working scale to be correct. Once the posts are in place then it is time to fill in the spaces between them with the planks, which are of a much thinner card. After given a little time for the glued pieces to set you can slide your knife blade, or similar, under the ends of the stuck down laterals and lift your fencing off the glass or out of the jig.
Now to add the finishing touch to the model we add end caps to the upright posts. These are just small squares of the thinner card, they are just about visibkle in the photograph and, as in the real thing, make all the difference to the appearance of the finished fencing.
If I intend to paint the card then I go over it with shellac first, before starting any cutting, but in this case it is supposed to be unpainted wood so I use an appropriate colour wood dye after the fence has been completed. If you know you are going to be using wood dye on any card model then do try your best to keep any glues away from the surface of the card which is to be dyed. The glue prevents the dye from soaking into the card and gives a patchy effect. Colron make a good range of wood dyes and I have found that black, mahogany and driftwood are the ones I use most but it is all down to personal choice. The driftwood colour is particularly good for very old weathered wood or that dilapidated old fence you are making. 
This final picture shows the line side fencing, the making of which is shown on another page, and the plank fencing installed on Barchester. Everything you see in this photograph has been hand made at an absolute minimum cost but the return in personal satisfaction and pleasure has been very high.
What is pictured here is not intended to show exact scale models of the real thing but rather quick and simply made objects for the model railway lineside. I only illustrate one method of building such things and it is up to you to apply the correct measurements for the particular scale you are working in.