Yes there are 2 salvages and they are to keep the fabric from raveling. That said I do not think it makes any difference which way you cut the fabric. Probably the most common way is to put salvages together and then cut WOF. The main reason for this maybe that it is easier to fold fabric salvage to salvage than a very long length of fabric end to end.. If you think about it your blocks are turned everyway when sewing them together. Also it may make a difference if you have a directional pattern Many people use lenght of fabric for the borders to keep them from stretching.