Knotted ropes come in a large variety. Also the length of the rope and the number of knots differs.
Somewhat common in continental Europe is a rope with 12 knots. The theory behind is that with such a rope you can construct a right angle, so the rope has a geometrical function.
But you also see ropes with 9 knots, or 7 or 3. For most numbers, people have come up with explanations.
The rope often borders the tracing board (either or not together with the angled border). There are lodges in France that have a rope with knots around the walls of the lodge room, which seems to be the same function.
The knots themselves are sometimes explained as ‘love knots’. ‘widows’s knots’ and sometimes the artist even drew other knots than just the famous flat knot. This either or not can have a significance as well.
The rope with knots is most common on “craft” tracing boards. It is sometimes called ” cord of union”.
Top: edited French tracing board. Feddersen also has it (F/25 p. 295) he gives as source the Manuel Maçonnique of Vuillaume, 1801.
Bottom: Wikimedia Commons