Gidday mate
Not sure what you mean by fence?An object? If so, it would depend on if the part itself had that parameter. Otherwise you may want to acquaint yourself with the rot() command in GDL.
As for the second question, load an add-on from your Goodies folder called Mesh To Roof. Do this from Tools>Add On Manager. Then you can use it for trimming.
That is, of course, if you don't want to use Solid Ops.
Cheers,
Link.
