Some patterns are not suitable for one way designs. A tote bag that does not have a bottom seam is an example of something that would not work with a one way design fabric. On a no-seam bottomed tote bag the fabric folds to form the other side of the bag, once folded the fabric is going a different direction and may appear upside down.
Because the fabric needs to go all in the same direction, it is necessary to buy the fabric amount that is called for under "with nap"
Another consideration when buying a fabric with a one way design is matching the design. It may be necessary to buy extra fabric to match the design. The size of the print and the number of times you will be able to use the width of the fabric guide your decision about how much extra to buy.
Never assume the fabric will be there if you need to come back for more.
