I am trying to picture the exact scenario, as in it is a wooden dock with no fencing around it but perhaps a wooden border of about a foot and 1/2 like a wharf. Some people have used wall hanging hooks that you screw into wood by hand that are $1 each. very effective on an old wooden dock where a couple small holes won't deface the old dock. They are made in a question mark shape and also a U shape.
If it is a deep dock, sometimes we just lay the rod flat on the edge and drop straight down with the drag loose enough to run out. Most docks usually have at least a small wooden railing on the perimeter, even the ones where ships pull up next to them and moor.
If anything, I would attach a rod-leash to anything stable on that dock if you don't keep your drag loose!