Years ago I bought a canoe, the ropes had several of these knots. I have never been able to replicate them (granted I have not tried a lot either).
Some other angles:

Years ago I bought a canoe, the ropes had several of these knots. I have never been able to replicate them (granted I have not tried a lot either).
Some other angles:

What is it supposed to do? It seems like come loose if you pull from one end and tight from another?
Unsure of its original purpose, but when I purchased the canoe, the seller belied me load it and we used trucker’s hitches going through the loops of these knots. From what I remember the loop did not slip when pulled, but if you pulled the tail the whole knot came undone.