18 meshes long will give you a net about 3'-0" using a standard mesh board (2").
I use the knot as described by Leeview when knitting with spun poly(or nylon in days gone by), don't know the name of the knot it's just the way i was taught over 30 years ago, it stops slip knots occurring and that can only be a good thing when learning.I use single knots when knitting hemp nets.
Finishing is just as easy as knitting the rows, instead of a mesh board you're using the front of the ring.
Good luck, it does get easier the more you do. . if you get stuck just give me a shout, i'm no expert nor a