The Spanish bowline is a double loop knot with each loop separately fixed. However the loops are directly connected to each other and you can adjust the loop sizes before putting them under pressure.
Spanish bowline can be made in the middle of a line and could be used for various purposes as long as the load on the loops is equal to avoid slipping.
Spanish bowline can be used to lift a person. For a conscious person, each loop is placed around a leg and the person holds onto the standing part of the rope. This knot can serve as a makeshift Bosun’s chair. For an unconscious person one loop is placed around the arm pits and the second loop is placed around the knees.
Carpenters use this knot to suspend a ladder.
Spanish bowline is a complicated knot and if not properly tightened, it can slip. This is because the loops are directly connected to each other. To avoid slipping make sure the loops are loaded equally and the knot is drawn very tight.