When cutting out fabric with nap it is necessary to cut the fabric so that it will all be running on one direction.
There are many new fabrics on the market that do not have pile but would require you to use the with nap lay out.
When in doubt there are a couple of ways to see if the fabric will need the "with nap" requirements.
- Brush the fabric with your hand one way and then brush the area next to that area the other way. Observe if the fabric looks the same when brushed in both directions.
- Using a length of fabric, fold the fabric lengthwise and lay the two directions next to each other. Observe if the fabric looks the same from each direction.