Why modelling them, just use the displacement trick i told you of.
View the image and follow the instructions below:
http://img831.imageshack.us/img831/678/disprailingtut.jpg1. place a straight brush with the railing texture on it on top of the railing
2. turn the sides top and front into displacements with the power of 2
3. use the "Paint geometry" tool to drag the vertex into possition beginning with the lowest vertex to avoid overlapping.
I used values of 14, 28, 42, 56 units for my railing, ofc. it depends on the situation.
Messure hight difference between your straight brush and the point where the railing should end at.
Next divide this value through 4 and you got your value 1, double and tripple it to get value 2 and 3.
Enter them into the Distance field of the disp paint tool, disable spatial and drag them down.
Maybe do this for every side seperatly, otherwise you might acidentally drag a vertex from the backside.
This technic isn't limited to railings, you can use it everywhere you need to align a texture to a diagonal surface and you don't wanna create a special texture or do it the cheap and ugly way by rotating. (see image 5)