There are a couple of schools of thought on the layout of jacklines.
The simple idea,
- From the stern to the bow along the sides of the boat either port/starboard or both.
- Down the center of the boat from cockpit to mast, then from mast to bow.
I promote style 2. The reason is simple. The center line keeps me further away from the boat edge. If I fall, I fall on the boat not over the side.
Along with the layout of the jack lines are the length of the tether, the way you attach to the jack line, how the jack lines are attached to the boat, and the harness you use.